Nanofibrillated Cellulose Ply Bonding Agent Or Adhesive and Multi-Ply Absorbent Sheet Made Therewith

ABSTRACT

A ply-bonding agent or adhesive composition characterized by a viscosity and a surface tension for the manufacture of paper tissue and paper towel, includes: (a) water; (b) nanofibrillated cellulose; and (c) one or more modifiers effective to modify either or both of (i) the viscosity of the composition or (ii) the surface tension of the composition, wherein the one or more additional modifiers are selected from the group consisting of components (iii), (iv), (v), (vi), (vii) or (viii), wherein: (iii) is PVOH and a viscosity modifier; (iv) is a viscosity modifier; (v) is a viscosity modifier and a surface tension modifier other than PVOH; (vi) is a water-soluble cellulose derivative; (vii) is a water soluble polyol; and (viii) is a surface tension modifier other than PVOH. The compositions are particularly useful for ply-bonding multi-ply absorbent sheet when the plies are treated with debonder.

CLAIM FOR PRIORITY

This application is based on U.S. Provisional Application No.62/280,161, filed Jan. 19, 2016, entitled Nanofibrillated CellulosePly-bonding Agent and Multi-Ply Absorbent Sheet Made Therewith and U.S.Provisional Application No. 62/366,154, filed Jul. 25, 2016 entitledConverting Process and Multi-Ply Absorbent Sheet with NanofibrillatedCellulose Ply-Bonding Adhesive as well as U.S. Provisional ApplicationNo. 62/366,137 filed Jul. 25, 2016 entitled Absorbent Sheet Tail Sealedwith Nanofibrillated Cellulose Containing Adhesives. The priorities ofthe foregoing applications are hereby claimed and their disclosuresincorporated herein by reference.

TECHNICAL FIELD

The present invention relates generally to multi-ply absorbent sheetply-bonding or adhesive compositions, wherein the plies are bonded toone another with a pseudoplastic composition provided withnanofibrillated cellulose. The plybonding compositions of the inventioninclude nanofibrillated cellulose and additional components such as aviscosity modifier in preferred embodiments. The plybonding compositionsof the invention develop increased plybond and are relativelyinsensitive to debonder content in the basesheet which enables higherconverting speed and productivity.

BACKGROUND

Nanofibrillated cellulose (NFC) or sometimes referred to asmicrofibrillated cellulose (MFC) is known in the art to be useful for avariety of purposes, including for use as a structural material in sheetand related articles. For example, in U.S. Pat. No. 6,734,335 it ismentioned that NFC is useful in absorbent structures. Col. 22, lines13+. See, also, U.S. Pat. No. 7,614,110, Col. 13, lines 38+. UnitedStates Patent Application Publication No. US 2012/0219816 discloses useof NFC as a layer in a multilayer paperboard structure, Abstract. See,generally, United States Patent Application Publication No. US2012/0058536, ¶ [0151], which discloses NFC as a structural material.NFC is used in molded structures, as seen in United States PatentApplication Publication No. US 2009/0308552, ¶ [0001], as well as UnitedStates Patent Application Publication No. US 2011/0263756, Abstract. NFCis, likewise, known for use in adhesives. JP 60250079 discloses a liquidadhesive made by blending a polyvinyl acetate emulsion, sodiumcarboxymethyl cellulose and above 3-4% NFC based on the weight of theliquid composition. See, also, United States Patent ApplicationPublication No. US 2010/0285295, ¶ [0023], where NFC is mentioned as afiller for an adhesive resin; United States Patent ApplicationPublication No. US 2011/0052881, ¶ [0062], having similar discussion, aswell as United States Patent Application Publication No. US2009/0042003, ¶ [0057].

United States Patent Application Publication No. US2015/0090156 of Combset al., entitled Adhesives That Include Plasticized Starch Derivativesand Methods and Articles Relating Thereto (Celanese Acetate LLC)disclose hot melt adhesive compositions based on starch, celluloseacetate and/or acetins and propose the use of cellulose nanofibrils asan optional filler and xanthan gum as an optional polymeric ingredient.

Multi-ply absorbent sheet such as towel and tissue sometimesconventionally include a plurality of glue-bonded layers or plies. Suchproducts are commercially produced on high speed converting lines withan adhesive to bond the plies. Adhesives employed include aqueouspolyvinyl alcohol (PVOH) solutions as is disclosed in U.S. Pat. No.3,414,459. Such solutions usually contain 4-10% by weight PVOH andexhibit Newtonian Fluid viscosity characteristics; that is, whereinviscosity is substantially independent of shear. Tissue/towelply-bonding is typically carried out in the following steps: 1)embossing one or more plies; 2) applying glue to the web on the raisedemboss pattern elements; 3) bringing one or more plies into contact withthe glued surface and applying sufficient pressure to the mated web toprovide enduring plybond once the glue has dried. This process placesseveral demands on the glue. It must penetrate the first web, but nottoo much. Enough tackiness must remain to stick to the non-glued web.The remaining glue must preferably penetrate the nonglued web to improvethe integrity of the bond. See, also, U.S. Pat. No. 5,858,554 to Neal etal., entitled Paper Product Comprising Adhesively Joined Plies whichdescribes ply-bonded absorbent sheet provided with polyvinyl alcohol orstarch adhesive compositions, note Col. 4, lines 20-55.

Conventional adhesives tend to adversely impact softness of the productdue to their inherent stiffness and their use in relatively highconcentration. Moreover, one of the most challenging obstacles of highspeed converting is that the loss of plybond causes ply separation andeventually stops the machine. Conventional plybond glues frequently donot generate enough plybond to enable higher speeds and are thus abottleneck to higher productivity, especially when debonder is used toprovide additional softness to the product.

SUMMARY OF INVENTION

Nanofibrillated cellulose together with one or more viscosity or surfacetension modifiers has been found to be a surprisingly effectiveply-bonding agent for absorbent sheet. Without intending to be bound byany theory, it is believed that NFC bonds two plies of tissue togetherby way of a “double ended nail” mechanism discussed hereinafter. Thismay be similar to the mechanism employed by the Velcro® strips fortemporarily plying two surfaces together. The forces involved in holdingadhesives to their substrates are mainly from adhesive and cohesiveforces. Adhesive forces hold two materials together at their surface,and cohesive forces are those forces that exist between molecules of thesame materials. For NFC bonding agent, both the bonding agent andsubstrate are made from cellulose, the adhesive and cohesive forces areconsistent and they are both hydrogen bonds. Hydrogen bonds are strongerbonds than Van der Waals forces which may be the force between celluloseand PVOH. Therefore, a comparable plybond can be formed by using NFCbonding agent at a much lower solids content (0.5-1% solids) than PVOHglue (4%-5% solids). NFC provides more surface area to connect the fiberand the plybond is achieved by mechanical contact force between the NFCand the basesheet. NFC thus serves as an alternative laminating agent toPVOH. It may be used at a significantly lower concentration than PVOHdue to its high viscosity, and offers advantages in terms of surfacefinish and texture, especially the softness of finished product, byavoiding using PVOH and by using less solids of adhesive.

The plybond of finished products converted with the NFC bonding agentswere found to be less sensitive to converting speed compared to theplybond converted with conventional PVOH glue. Therefore, using theinvention NFC bonding agent allows for increased productivity withoutsacrificing plybond while obtaining improved softness (less marryingroll pressure, less glue) as noted above. The adhesives are particularlyadvantageous with debonder treated sheet because they maintain superiorplybond in the presence of debonder.

The invention is appreciated by reference to FIG. 1A and FIG. 1B, whichare histograms showing Peel Test Plybond for CWP and Structuredbasesheet. It is seen that a 1% NFC/0.1% xanthan gum bonding agent and a0.5% NFC/0.1% xanthan gum bonding agent have Peel Test Plybond valuesremarkably higher than a 2.5% PVOH composition.

The invention is further appreciated by reference to FIGS. 2A, 2B and 2Cwhich are histograms comparing Peel Test Plybond of various compositionsof the invention with 4.5% PVOH plybond adhesive. FIG. 2A shows that NFCbonding agent has very good laminating properties compared to 4.5% PVOH.0.5% NFC-0.1% xanthan gum developed a plybond which was approximately22% lower than 4.5% PVOH, while 1% NFC-0.1% xanthan gum formed theplybond 44% higher than 4.5% PVOH. Therefore, a certain NFCconcentration between 0.5% and 1% should provide the same plybond as4.5% PVOH. In addition, the Figures show that the bonding strength wasmainly from NFC because it is seen that xanthan gum itself was a weakadhesive; 1% xanthan gum's plybond was 10.7 g while 1% NFC-0.1% xanthangum laminating agent has a plybond of 34.9 g. Xanthan gum's majorfunctions are as suspending agent and viscosity modifier. It isdesirable to use the minimum amount of xanthan gum as long as it caneffectively disperse and suspend NFC to obtain an appropriate viscosity.Unlike conventional uses of xanthan gum as a thickener, its use with NFCreduces the viscosity of the bonding agent dispersion. Additionaladvantages of xanthan gum are that it is inexpensive and safe (foodgrade). Alternative food-grade viscosity modifiers which have propertiessimilar to xanthan gum are also suitable. The plybond of NFC-CMClaminating agent and NFC-pectin (from apple) laminating agent weretested for Peel Test Plybond. Details as to specific ingredients arediscussed below. The results showed that they were somewhat lesseffective than xanthan gum at the same dosage in terms of plybondstrength (FIGS. 2B and 2C). According to the viscosity results discussedherein, pectin does not as effectively reduce the viscosity ofNFC-pectin bonding agent as xanthan gum, while NFC-CMC may besubstituted for xanthan gum if the cost of CMC is significantly lowerthan xanthan gum and strong plybond is not a requirement for thefinished product.

In addition to the benefits seen in terms of ply-bonding and softness,the use of low solids adhesive also reduces converting costs and mightalso provide advantage in cleaning the glue from the surface ofconverting equipment.

The present invention is thus directed, in part, to an aqueousplybonding adhesive including: (a) water; (b) nanofibrillated cellulose;and (c) one or more modifiers effective to modify either or both of (i)the viscosity of the composition or (ii) the surface tension of thecomposition, wherein the one or more additional modifiers are selectedfrom the group consisting of components (iii), (iv), (v), (vi), (vii) or(viii), wherein: (iii) is PVOH and a viscosity modifier; (iv) is aviscosity modifier; (v) is a viscosity modifier and a surface tensionmodifier other than PVOH; (vi) is a water-soluble cellulose derivative;(vii) is a water soluble polyol; and (viii) is a surface tensionmodifier other than PVOH.

Further features and advantages of the invention will be apparent fromthe discussion which follows.

BRIEF DESCRIPTION OF DRAWINGS

The invention is described in detail below with reference to thedrawings wherein:

FIG. 1A is a histogram detailing Peel Test Plybond for various bondingagent formulations applied to CWP basesheet;

FIG. 1B is a histogram detailing Peel Test Plybond for various bondingagent formulations applied to a Structured basesheet;

FIG. 2A is a histogram detailing Peel Test Plybond for various bondingagent formulations applied to a Structured basesheet;

FIG. 2B is a histogram detailing Peel Test Plybond for various bondingagent formulations applied to a Structured basesheet;

FIG. 2C is a histogram detailing Peel Test Plybond for various bondingagent formulations applied to a Structured basesheet;

FIG. 3 is a schematic diagram of an embossing and laminating apparatusfor preparing multi-ply absorbent sheet;

FIG. 4 is a diagram showing the pattern of raised embossments providedto the tissue basesheet by the apparatus of FIG. 3;

FIGS. 5A and 5B are plots of plybond strength versus converting speed;

FIG. 6 is a plot of viscosity versus shear rate for various adhesives;

FIGS. 7A and 7B are histograms of plybond strength for differentproducts at different converting speeds;

FIGS. 8A and 8B are plots of panel softness (arbitrary scale) forvarious products;

FIG. 9 is a perspective view of a three-ply product;

FIG. 10 is a schematic diagram illustrating ply-bonding of the inventionmaterial and conventional PVOH glue;

FIGS. 11A and 11B are scanning electron micrographs of NFC;

FIG. 12 is a plot of Cellulose Nanofiber Viscosity versus shear rate forNFC I and NFC II;

FIG. 13 is a histogram detailing breaking length for NFC I and NFC IIformed into handsheets or films;

FIG. 14 is a histogram detailing maximum stretch, or stretch at breakfor NFC I and NFC II, formed into handsheets or film;

FIG. 15A is a plot showing the surface tension of NFC, tap water andxanthan gum;

FIG. 15B is a plot showing the surface tension of various compositions;

FIGS. 16 and 17 are plots of Adhesive Viscosity versus shear rate forvarious adhesives;

FIGS. 18-21 are plots of Viscosity versus shear rate for variousply-bonding adhesives and components thereof;

FIG. 22 is a histogram of Peel Test Plybond for various adhesives andbasesheets with and without debonder;

FIG. 23 is a plot showing the effect of converting speed on plybond withNFC containing ply-bonding adhesive;

FIG. 24 is a plot showing the effect of converting speed on plybond withregular PVOH glue and NFC containing ply-bonding adhesive;

FIG. 25 is a diagram of an arabesque line emboss pattern for TAD towel;

FIG. 26 is a plot comparing plybond of multi-ply sheet made with regularPVOH glue and NFC containing ply-bonding adhesive;

FIG. 27 is a plot comparing plybond and converting speed for regularPVOH glue and NFC containing poly-bonding adhesive; and

FIG. 28 is a plot comparing plybond and converting speed of regular PVOHglue and NFC containing poly-bonding adhesive.

DETAILED DESCRIPTION

The invention is described in detail below in connection with theFigures for purposes of illustration, only. The invention is defined inthe appended claims. Terminology used herein is given its ordinarymeaning consistent with the exemplary definitions set forth immediatelybelow; mg refers to milligrams and m² refers to square meters, Fpmrefers to feet per minute and so forth.

Adhesive Viscosity is measured at room temperature using a cone andplate geometry.

Characteristic Breaking Length of NFC material is determined by testinga handsheet of the subject NFC fiber as described herein.

Characteristic Nanofiber Viscosity is measured on a 1 wt % suspension ofthe NFC in water as further described herein.

“Consisting essentially of” and like terminology refers to the recitedcomponents and excludes other ingredients which would substantiallychange the basic and novel characteristics of the composition orarticle. Unless otherwise indicated or readily apparent, a compositionor article consists essentially of the recited or listed components whenthe composition or article includes 90% or more by weight of the recitedor listed components. That is, the terminology excludes more than 10%unrecited components.

“Converting speed” refers to the linear velocity of the basesheets andmulti-ply product through a converting or laminating line as is seen inFIG. 3.

A surface tension modifier refers to an agent effective to reduce thesurface tension of an aqueous composition of the invention. The additionof surface tension modifier is optional depending on the needs of theapplication. Typically, a suitable surface tension modifier is used inamounts effective to reduce the surface tension of the same compositionwithout a surface tension modifier by at least about 10 mN/m, preferablyby 15 mN/m, 20 mN/m or more. The same composition without a surfacetension modifier refers to a composition with the same ingredients andproportions except that the surface tension modifier is absent.

A viscosity modifier refers to an agent effective to reduce theviscosity of an aqueous composition including NFC. Preferred viscositymodifiers are effective to reduce the room temperature viscosity of a 1%NFC aqueous composition by at least 750 cP at a shear rate of 100 s⁻¹when added to the composition at a level of 0.1% by weight of theaqueous composition.

Cellulosic Sheet, Components and Related Terminology

The term “cellulosic”, “cellulosic sheet” and the like are meant toinclude any product incorporating papermaking fiber having cellulose asa major constituent. “Papermaking fibers” include virgin pulps orrecycle (secondary) cellulosic fibers or fiber mixes comprisingcellulosic fibers. Fibers suitable for making the webs of this inventioninclude: nonwood fibers, such as cotton fibers or cotton derivatives,abaca, kenaf, sabai grass, flax, esparto grass, straw, jute hemp,bagasse, milkweed floss fibers, and pineapple leaf fibers; and woodfibers such as those obtained from deciduous and coniferous trees,including softwood fibers, such as northern and southern softwood Kraftfibers; hardwood fibers, such as eucalyptus, maple, birch, aspen, or thelike. Papermaking fibers used in connection with the invention aretypically naturally occurring pulp-derived fibers (as opposed toreconstituted fibers such as lyocell or rayon) which are liberated fromtheir source material by any one of a number of pulping processesfamiliar to one experienced in the art including sulfate, sulfite,polysulfide, soda pulping, etc. The pulp can be bleached if desired bychemical means including the use of chlorine dioxide, oxygen, alkalineperoxide and so forth. The products of the present invention maycomprise a blend of conventional fibers (whether derived from virginpulp or recycle sources) and high coarseness lignin-rich tubular fibers,such as bleached chemical thermomechanical pulp (BCTMP). Pulp-derivedfibers thus also include high yield fibers such as BCTMP as well asthermomechanical pulp (TMP), chemithermomechanical pulp (CTMP) andalkaline peroxide mechanical pulp (APMP). “Furnishes” and liketerminology refers to aqueous compositions including papermaking fibers,optionally wet strength resins, debonders and the like for making paperproducts.

Kraft softwood fiber is low yield fiber made by the well-known Kraft(sulfate) pulping process from coniferous material and includes northernand southern softwood Kraft fiber, Douglas fir Kraft fiber and so forth.Kraft softwood fibers generally have a lignin content of less than 5percent by weight, a length weighted average fiber length of greaterthan 2 mm, as well as an arithmetic average fiber length of greater than0.6 mm.

Kraft hardwood fiber is made by the Kraft process from hardwood sources,i.e., eucalyptus and also has generally a lignin content of less than 5percent by weight. Kraft hardwood fibers are shorter than softwoodfibers, typically having a length weighted average fiber length of lessthan 1 mm and an arithmetic average length of less than 0.5 mm or lessthan 0.4 mm.

Recycle fiber may be added to the papermaking furnish in any amount.While any suitable recycle fiber may be used, recycle fiber withrelatively low levels of ground wood is preferred in many cases, forexample recycle fiber with less than 15% by weight lignin content, orless than 10% by weight lignin content may be preferred depending on thefurnish mixture employed and the application. Recycle fiber is in manycases 80% hardwood fiber.

“Basesheet” refers to a unitary cellulosic sheet as manufactured by apaper machine. Basesheets may be layered; however, they have a unitarystructure not readily delaminated. A “ply” of a finished product refersto basesheet incorporated into the product.

Unless otherwise specified, “basis weight”, BWT, bwt, and so forthrefers to the weight of a 3000 ft² ream of product. Consistency refersto percent solids of a nascent web, for example, calculated on a bonedry basis. “Air dry” or simply “dry” means including residual moisture,by convention up to about 10 percent moisture for pulp and up to about 6percent for paper. A nascent web having 50 percent water and 50 percentbone dry pulp has a consistency of 50 percent.

Products of the invention are made with a cellulosic fiber basesheet andhave an absorbency or SAT value as well as tensiles and densitiessuitable for tissue and towel products. Typical SAT values are greaterthan about 3 g/g in most cases. See U.S. Pat. No. 8,778,138.

“CWP” refers to absorbent products made by a conventional wet-pressprocess; that is, wet-pressing a furnish to a drying cylinder with apapermaking felt followed by creping the web from the cylinder. See U.S.Pat. No. 7,951,266, FIG. 7 thereof.

“Structured” basesheet refers to product that is wet creped (fabriccreped) from a cylinder prior to final drying. See U.S. Pat. Nos.7,850,823; 7,585,388; 7,585,389; and 7,662,257.

“TAD” refers to through-air dried absorbent products. Throughdried,creped products are disclosed in the following patents: U.S. Pat. No.3,994,771 to Morgan, Jr. et al.; U.S. Pat. No. 4,102,737 to Morton; andU.S. Pat. No. 4,529,480 to Trokhan. The processes described in thesepatents comprise, very generally, forming a web on a foraminous support,thermally pre-drying the web, applying the web to a Yankee dryer with anip defined, in part, by an impression fabric, and creping the productfrom the Yankee dryer.

The absorbent characteristics of a product can be affected by thefurnish, basis weight, strength, papermaking technology, and so forth.The sheet absorbency and converting technology for a specific productwill impact the selection of bonding agent characteristics. CWP sheetsare more consolidated than TAD sheets and therefore may have a lowerwicking rate. Towel sheets commonly contain more softwood than tissuesheets, which may impact the pore size distribution of the web. It canbe appreciated that an optimal bonding agent formula for one product maynot be optimal for another.

A towel product is typically characterized by having predominantly (morethan 50% by weight based on fiber content) softwood fiber.

A tissue product is typically characterized by having predominantly(more than 50% by weight based on fiber content) hardwood fiber.

Ply-bonding adhesive composition may be described in terms of percentsolids or other ingredient based on the total weight of the ply-bondingcomposition. A composition described as 1% NFC and 0.1% xanthan gum thushas 1% NFC, 0.1% xanthan gum and the balance of 98.9% water and otheroptional ingredients. Two bonding agents generally comparable to acontrol glue at 4.5% PVOH solids are a bonding agent 1 (CH1) comprisedof 2% PVOH+0.5% NFC, and NFC bonding agent 2 (CH2) comprised of 2.3%PVOH+0.6% NFC+0.1% xanthan gum.

Alternatively, it is sometimes convenient to express the amount of NFCin compositions with relatively high levels of PVOH content in terms ofPVOH solids, which is particularly convenient for bonding agents withrelatively high weight ratios of PVOH/NFC. 3% PVOH glue should beunderstood as 3 grams of PVOH per 100 grams solution. NFC addition maythen be described as a percentage of the PVOH in the formula. Thus, “3%PVOH+5% NFC based on PVOH content” means that the glue has 3 grams PVOHand 3*0.05=0.15 g NFC per 100 grams solution.

Representative compositions have one or more features enumerated inTables 1A through 1C and Table 2 below and may consist essentially ofthe listed components optionally with ranges adopted from another tableas discussed herein or by omitting a particular feature such as wt % ofone component or weight ratios of two components. The various ranges inTables 1A through 1C and Table 2 may be combined or interchanged betweencompositions as to various ingredients, that is, a general content rangeas to wt % PVOH content in one table may be matched with a selectcontent range of NFC wt % content in the same or another table in aparticular embodiment of the invention, in which case the weight ratioslisted in the following tables may be inapplicable to the particularembodiment contemplated. For example, a general content range as to wt %PVOH content in Table 1B may be matched with a select content range NFCwt % content in Table 1C. Likewise the wt % ranges in Table 2 for NFCcontent may be applied to any of the wt % ranges in Tables 1A-1C as toPVOH content in an aqueous composition and the weight ratiosre-calculated.

TABLE 1A PVOH/NFC Compositions Content Ranges Component General TypicalPVOH (wt %)   1%-7.5% 1.5%-6% NFC (wt %) 0.005%-3.75%   0.01%-1.5% Water90%-99%    94-98.5% (wt %) NFC 0.5%-50%    1%-25% (% based on PVOH)Weight Ratio 0.0007-3.75  0.015-1.5  NFC/PVOH Other Additives balancebalance

TABLE 1B PVOH based/NFC containing Compositions Content Ranges ComponentGeneral Typical Select PVOH (wt %)   2%-7.5% 2.5%-6%   3%-5% NFC (wt %)0.01%-1.5% 0.04%-0.75% 0.1%-0.5% Water  90%-98%    94-97.5% 95%-97% (wt%) NFC  1%-20%  1.5%-12.5%  4%-11% (% based on PVOH) Weight Ratio0.001-0.75 0.007-0.3  0.02-0.17 NFC/PVOH Other Additives balance balancebalance

TABLE 1C NFC and PVOH containing Bonding Compositions Content RangesComponent General Typical Select PVOH (wt %) 1%-3% 1.5%-2.5% 1.75%-2.5% NFC (wt %) 0.25%-1%   0.3%-0.8%  0.4%-0.75% Viscosity modifier   0-0.2%  0.0-0.15% 0.05%-0.15% (wt %) Water 95%-99% 95%-99% 96%-99% (wt %) NFC 8%-100% 12%-53% 16%-43% (% based on PVOH) Weight Ratio 0.08-1   0.1-0.50.15-0.4  NFC/PVOH Other Additives balance balance balance

TABLE 2 NFC/Viscosity Modifier Bonding Compositions Content RangesComponent General Typical Select NFC (wt %) 0.15%-3%   0.175%-2%   0.2%-1%   Viscosity modifier 0.02%-0.2% 0.05%-0.15% 0.07%-0.13%   (wt %)Weight Ratio   150-0.75  40-1.2 14-1.5  NFC:Viscosity Modifier Water (wt%)   95%-99.9%   97%-99.8% 98%-99.8% Other Additives balance balancebalance

Debonder compositions including surfactants are widely used in the paperindustry. There is disclosed in U.S. Pat. No. 7,736,464 to Kokko adebonder composition including a combination of: (a) a quaternaryammonium surfactant component; and (b) a nonionic surfactant component.In many cases, these compositions include a quaternary ammoniumsurfactant component comprising a surfactant compound selected from thegroup consisting of a dialkyldimethyl-ammonium salt of the formula:

a bis-dialkylamidoammonium salt of the formula:

a dialkylmethylimidazolinium salt of the formula:

wherein each R may be the same or different and each R indicates ahydrocarbon chain having a chain length of from about twelve to abouttwenty-two carbon atoms and may be saturated or unsaturated; and whereinsaid compounds are associated with a suitable anion; and (b) a nonionicsurfactant component that preferably includes a surfactant selected fromthe group consisting of alkoxylated fatty acids and alkoxylated fattyalcohols. Typically the nonionic surfactant includes the reactionproduct of a fatty acid or fatty alcohol with ethylene oxide such as apolyethylene glycol diester of a fatty acid (PEG diols or PEG diesters).One preferred composition which is used in connection with the presentinvention includes 30 wt % of imidazolinium (Im+) quats in a 1:1 mixtureof PEG-400-mono and dioleates.

The quaternary ammonium surfactant component most preferably includes animidazolinium salt. Other debonder compositions are disclosed in thefollowing references: U.S. Pat. No. 5,622,597 to Callen et al.; U.S.Pat. No. 4,441,962 to Osborn, III and U.S. Pat. No. 4,351,699 also toOsborn, III; U.S. Pat. No. 5,698,076 to Phan et al.; U.S. Pat. No.5,730,839 to Wendt et al.; U.S. Pat. No. 5,753,079 to Jenny et al.; U.S.Pat. No. 4,447,294 to Osborn, III; U.S. Pat. No. 5,279,767 to Phan etal. and U.S. Pat. No. 5,240,562 of Phan et al. Debonder applied to theabsorbent sheet is expressed on a dry basis of pounds debonder/ton ofpapermaking fiber in the absorbent sheet.

Debonder may be applied to the sheet by any suitable method such asspraying or more typically by way of adding the debonder to the aqueousfurnish in the headbox of a papermaking machine used to produce thesheet. In cases where a multilayer headbox is used to produce plieshaving multiple layers, treatment levels of debonder apply to any layerprovided to the sheet. For example, if one layer has no added debonder(other than perhaps residual debonder in the water provided to thefurnish) and another layer is treated at 4 lbs debonder/ton ofpapermaking fiber in the sheet, then the basesheet is considered to betreated at a level of 4 lbs debonder/ton.

Embossing and Laminating Multi-Ply Absorbent Sheet

Referring to FIG. 3, there is shown a converting apparatus 10 forembossing and plying basesheet into a multi-ply product. Apparatus 10includes a glue chamber 12, an anilox roll 14, an applicator roll 16, anembossing roll 18, a marrying roll 20 and an upper rubber roll 22 whichis softer than marrying roll 20 which is made of hard rubber.

In operation, a first basesheet 24 is fed to the nip between upper roll22 and embossing roll 18 where sheet 24 is provided with a plurality ofraised embossments having the pattern shown in FIG. 4. The pattern ofFIG. 4 provides an embossed area of raised embossments of 4.3% of thesheet area, which corresponds to the bonding area as will be appreciatedfrom the discussion which follows. Glue, including the NFC bondingagents of this invention is provided as an aqueous composition to gluechamber 12 and is picked up by anilox roll 14 and transferred toapplicator roll 16. From applicator roll 16, the glue is applied to theraised embossments of basesheet 24. Concurrently with processingbasesheet 24, a second basesheet 26 is fed through the nip defined bymarrying roll 20 and embossing roll 18 such that basesheet 26 is pressedto basesheet 24, including the adhesive disposed on the raisedembossments on basesheet 24, to produce multi-ply web 30.

Apparatus 10 was operated as described above to produce a variety ofmulti-ply tissue products. The apparatus was operated at convertingspeeds of 1000 fpm and 1500 fpm with tissue basesheet which consistedpredominantly of hardwood fiber. Details as to finished product andbasesheet properties appear in Tables 3 and 4. Adhesive compositions arenoted below.

The plybond was consistent over the given machine setting and its rangecould be controlled in a very similar way as that of the traditionalglue. Two bonding agents were tested against the control glue at 4.5%PVOH solids. The NFC bonding agent 1 (CH1) consisted of 2% PVOH+0.5%NFC, and NFC bonding agent 2 (CH2) comprised of 2.3% PVOH+0.6% NFC+0.1%xanthan gum. Two speed levels were tested for each of the bonding agentsas shown in FIGS. 5A and 5B.

The traditional PVOH glue utilized for laminating the control consistsof 4.5% PVOH solids. However, CH1 and CH2 chemistries of the bondingagent utilized PVOH solids at 2% and 2.3%, respectively. The usage ofPVOH may be avoided by alternative chemicals which are effective onreducing surface tension, as is discussed, below. Samples laminatedusing the NFC bonding agent chemistries showed satisfactory levels ofsoftness in the sensory evaluation. While producing these samples, themarrying roll was used to put pressure on the plies to set the bond.

TABLE 3 Finished Product Physicals (1000 fpm) Basis Caliper Weight 8Sheet GM Tensile Stretch Perf Tensile Stretch TMI lb/3000 mils/ TensileCD CD Tensile MD MD Plybond Sensory Description ft{circumflex over ( )}28 sht g/3 in g/3 in % g/3 in g/3 in % g Softness CONTROL 26.73 132.66839.31 629.75 7.48 532.44 1,118.61 23.68 9.25 18.30 STRUCTURED SHEET CH127.40 122.64 886.85 650.95 7.40 601.87 1,208.23 22.97 9.54 18.00STRUCTURED SHEET CH2 27.63 128.29 816.52 598.90 7.82 531.97 1,113.2322.38 7.44 18.30 STRUCTURED SHEET CWP Control 23.10 100.56 783.78 457.595.17 484.76 1,342.48 18.72 11.76 17.30 CH1 CWP 22.99 92.73 753.13 493.776.50 477.50 1,148.71 15.53 7.49 17.30 CH2 CWP 23.20 93.07 766.93 493.476.38 491.30 1,191.93 16.93 9.50 17.20

TABLE 4 Basesheet Properties Basis Caliper Break Break Break T.E.A.T.E.A. Weight 8 Sheet Tensile Tensile Tensile Stretch Stretch Mod ModMod MD CD lb/3000 mils/ MD CD GM MD CD GM MD CD mm-g/ mm-g/ Descriptionft{circumflex over ( )}2 8 sht g/3 in g/3 in g/3 in % % g/% g/% g/%mm{circumflex over ( )}2 mm{circumflex over ( )}2 Structured 13.77 58.73703.81 406.00 534.55 25.22 6.52 41.57 28.05 61.61 1.23 0.18 Sheet UnEmb#2 Structured 13.28 60.00 542.78 348.82 435.12 24.69 7.41 32.23 21.9947.24 0.94 0.18 Sheet Emb #3 CWP Unemb 11.08 31.30 631.25 290.26 428.0516.82 4.24 51.60 39.18 67.96 0.73 0.08 CWP Emb 12.21 34.43 739.85 274.36450.54 19.45 7.26 38.25 38.95 37.57 1.01 0.16

As shown in FIG. 6, the viscosity of 4.5% PVOH and NFC bonding agentswere within a similar range at the converting speed (the correlatedshear rate is in the range of 100 to 1000 s⁻¹). The viscosity modifierwas able to suspend the NFC particles through the glue pumping unitwithout causing coagulation in the glue tank.

For the products in Table 3, the tissue plybond target was 5 to 8 g, andall the products met the plybond target. At the same convertingsettings, the increase of converting speed typically results in asignificant decrease of plybond when using regular PVOH glue. The dropof plybond might be due to the reduced diffusion time of the PVOHpolymers in to the basesheet. When using 4.5% PVOH, by increasing theconverting speed from 1000 fpm to 1500 fpm, the plybond of CWP tissuedecreased from 11.8 g to 9.8 g which was a 16% decrease while structuredtissue suffered more where the plybond was dropped from 9.2 g to 5.5 gwhich was a 41% decrease. However, by using the NFC bonding agent, thespeed associated plybond decrease was significantly minimized as can beseen from FIGS. 7A and 7B. There were no significant differences inplybond between 1000 fpm and 1500 fpm for CWP tissue when using both NFCbonding agents CH1 and CH2 for converting. The plybond of structuredsheet was always more sensitive to converting speed, but using CH2resulted in 20% plybond reduction from 1000 fpm to 1500 fpm whereas the4.5% PVOH had 41% plybond reduction. NFC may provide an enhancedlocalized fiber density at the embossed area and tiny fibrils arethought to play an important role in bridging the two basesheets.

Typically, increasing the converting speed causes several issues. One ofthe major problems is that the plybond decreases significantly.Therefore, increasing marrying roll pressure or applying more glue isneeded to bring up the plybond. Both adjustments could result in reducedsoftness. The smaller sensitivity of NFC bonding agent to convertingspeed has an advantage of speeding up the converting speed withoutsacrificing product quality which enables improved productivity.

There was also a difference in plybond strength between the NFC bondingagent CH1 and CH2. For the CWP basesheets, the rolls converted by CH1and CH2 had the same converting settings (marrying roll), the plybondformed by CH2 was approximately 30% stronger than the plybond formed byCH1. This may be due to the higher solids content or that xanthan gumdispersed NFC in a more uniform way.

It was found that the converting speed did not affect softness. Most ofthe product converted at 1000 fpm and 1500 fpm had the same softness.For the same type of basesheet, the GM tensile of converted product wasin a narrow range, and the slightly varied GM tensile had little impacton softness. See Table 5 and FIGS. 8A and 8B.

TABLE 5 Softness 1000 fpm 1500 fpm GM Tensile, Sensory GM Tensile,Sensory Description g/3″ Softness g/3″ Softness CONTROL 839 18.3 80918.4 STRUCTURED CH1 887 18.0 — — STRUCTURED CH2 816 18.3 802 18.3STRUCTURED CWP Control 784 17.3 777 17.2 CH1 CWP 753 17.3 735 17.3 CH2CWP 766 17.2 754 17.2

Three-Ply Products

In some preferred embodiments, the present invention relates tothree-ply products such as three-ply tissue products as shown in FIG. 9.A three-ply product 35 includes a first outer ply 38, a central ply 40and a second outer ply 42. The plies are adhered together by PVOH/NFCadhesive interposed between the plies at their interfaces indicated at44, 46. Three-ply products may be made by successive lamination of theplies or by way of simultaneous lamination as is known in the art. Towelproducts may likewise be produced as three-ply absorbent structures, ifso desired.

There is no simple theory of adhesion, for any one system adhesion isprobably a combination of adsorption, electrostatic attraction anddiffusion. The enhancement of the bond between two plies might beexplained by ‘double ended nail’ mechanism that takes place between theNFC and the tissue basesheet (FIG. 10). The NFC acts like a nailsticking between the two “walls” of tissue. Each end of the nano fibrilis bonded with the tissue basesheet through a hydrogen bond. Themagnitude of this bond is stronger than the van der Waals bond butweaker than the covalent bond. Since the NFC is basically cellulose andthe basesheet is composed of cellulose, the large surface area NFC has apotential to form strong hydrogen bonds with the basesheet. According toprevious lab experimentation, it was found that the NFC bonding agentcould form stronger plybond with much less solids content than that ofPVOH glue. It is also proposed that the NFC preserves the softness ofconverted product compared to that by the polymer matrix such as PVOH. Astable suspension and acceptable shelf life was seen to be obtained byadding viscosity modifier and antibacterial agent to the new NFClaminating agent.

Further details concerning materials, adhesive formulation and testingare described below.

Testing

Dry tensile strengths, stretch, ratios thereof, modulus, break modulus,stress and strain are measured with a standard Instron test device orother suitable elongation tensile tester which may be configured invarious ways, typically using 3 or 1 inch wide strips of material,suitably conditioned in an atmosphere of 23°±1° C. (73.4°±1° F.) at 50%relative humidity for 2 hours. This conditioning method is preferablyemployed for all specimen testing. The tensile test is typically run ata crosshead speed of 2 in/min. Tensile strength is sometimes referred tosimply as “tensile” and is reported herein for NFC as breaking length(km), which is the tensile in kg/m divided by the basis weight of thesample in g/m². See U.S. Pat. No. 8,409,404 for additional measurementsand details.

The term “Characteristic Breaking Length” when referring to NFC refersto the breaking length of a handsheet or film made from 100% of the NFC.The handsheet (50-70 g/m²) is made by using vacuum filtration and asuitable membrane as is described in more detail hereinafter followed byrestrained air drying.

The modulus of a specimen (also referred to as stiffness modulus ortensile modulus) is determined by the procedure for measuring tensilestrength described above, using a sample with a width of 1 inch, and themodulus recorded is the chord slope of the load/elongation curvemeasured over the range of 0-50 grams load. The specific modulus is themodulus divided by density.

Characteristic Nanofiber Viscosity and Bonding Agent Viscosity

Characteristic Nanofiber Viscosity is measured on a 1 wt % suspension ofthe subject NFC in water.

Viscosity of the glues and NFC suspensions is measured at roomtemperature, using a TA instruments Discovery Hybrid Rheometer (DHR) 2.A cone and plate geometry was used for analysis. A few drops of samplewere placed on a flat metal peltier plate and the cone spindle, whichhas a 60 mm diameter and 2° angle, was brought down to make contact withthe sample to initiate the spreading action. The sample that flowed outof the circumference of the cone spindle was trimmed. The experimentalconditions were as follows: flow logarithmic sweep, shear rate 0.5-2000Hz at room temperature. Trim and geometric gap was 54 microns. Roomtemperature means ambient temperature between 23° C. and 29° C.,typically. If a specific value is required, 25° C. is used.

Peel Test Plybond

In order to characterize the adhesive strength of each glue, a strip ofstructured basesheet was adhered to a metal plate followed bymeasurement of the force required to peel the sheet off. Ten drops ofglue approximately 0.5 g was evenly spread on a 2″×8″ stainless steeltest panel plate using a number 40 wire rod to apply a film ofapproximately 50 microns, followed by attaching a 2″×12″ basesheet, tothe glued plate surface and pressing it from one end to another for 3times using a metal roller. After drying the glued structured basesheet,the plybond between basesheet and steel plate was measured by a peelingtest using an Instron tensile test machine 5966. The free end of thebasesheet strip was separated by hand for 2″. The specimen was placed inthe testing machine by clamping the steel plate in the bottom grip andturning up the free end of the basesheet and clamping it in the uppergrip. The peeling test was performed by stripping the basesheet from thesteel plate approximately at an angle of 180° and a ramp rate of 10″/minfor 10″ displacement. At least 6 specimens were tested for each gluesample. After each test, the steel plate was washed with DI water andacetone to remove the residual glue before the next use. These tests aregenerally in accordance with test method ASTM D 903-98 except for thedifferences noted.

Plybond

Generally the force needed to separate a ply of a multi-ply sheet orPlybond is measured with a Lab Master Slip and Friction tester availablefrom Testing Machines, Inc. (Islandia, N.Y.) fitted with a sample clampplatform available from Research Dimensions (Neenah, Wis.). A top ply ofthe sample is separated and clamped in a clamp attached to a load celland the average force required to separate the ply from another ply isrecorded as the plies are separated. Details appear below for 2-plytesting; while 3-ply testing is substantially the same.

Plybond strengths reported herein are determined from the average loadrequired to separate the plies of two-ply tissue, towel, napkin, andfacial finished products using TMI Plybond Lab Master Slip & Frictiontester Model 32-90, with high-sensitivity load measuring option andcustom planar top without elevator available from: Testing Machines Inc.2910 Expressway Drive South Islandia, N.Y. 11722; (800)-678-3221;www.testingmachines.com. Plybond clamps are available from: ResearchDimensions, 1720 Oakridge Road, Neenah, Wis. 54956, Contact:920-722-2289 and Fax: 920-725-6874.

Samples are preconditioned according to TAPPI standards and handled onlyby the edges and corners care being exercised to minimize touching thearea of the sample to be tested.

At least ten sheets following the tail seal are discarded. Four samplesare cut from the roll thereafter, each having a length equivalent to 2sheets but the cuts are made ¼″ away from the perforation lines bymaking a first CD cut ¼″ before a first perforation and a second CD cut¼″ before the third perforation so that the second perforation remainsroughly centered in the sheet. The plies of the each specimen areinitially separated in the leading edge area before the firstperforation continuing to approximately ½″ past this perforation.

The sample is positioned so that the interior ply faces upwardly, theseparated portion of the ply is folded back to a location ½″ from theinitial cut and ¼″ from the first perforation, and creased there. Thefolded back portion of the top ply is secured in one clamp so that theline contact of the top grip is on the perforation; and the clamp isplaced back onto the load cell. The exterior ply of the samples issecured to the platform, aligning the perforation with the line contactof the grip and centering it with the clamp edges.

After ensuring that the sample is aligned with the clamps andperforations, the load-measuring arm is slowly moved to the left at aspeed of 25.4 cm/min, the average load on the arm (in g.) is measuredand recorded. The average of 3 samples is recorded with the fourthsample being reserved for use in case of damage to one of the firstthree. See U.S. Pat. No. 8,287,986.

Nanofibrillated Cellulose

NFC is commonly produced by mechanically disintegrating wood pulp, suchas hardwood or softwood Kraft pulp which can include chemical pre- orpost-treatments. The pulp used may be pre-processed enzymatically orchemically, for example, to reduce the quantity of hemicellulose.Furthermore, the cellulose fibers may be chemically modified, whereinthe cellulose molecules contain functional groups other than in theoriginal cellulose. Such groups include, among others, carboxymethyl(CMC), aldehyde and/or carboxyl groups (cellulose obtained by N-oxylmediated oxidation, for example “TEMPO”), or quaternary ammonium(cationic cellulose).

Generally, a high shear zone is formed during disintegration todelaminate multilayer cell walls of wood fibers and separate fibrilswhile minimizing cutting and entangling. This process is used to isolatehigh aspect ratio, semi-crystalline cellulose fibrils with robustmechanical properties from the wood furnish. Nanofibrils are typicallyon the order of 4-20 nm wide and 500-2000 nm long. They possess goodaxial tensile strength due to inter- and intra-molecular hydrogenbonding among highly oriented cellulose molecules. Various processessuitable for making NFC are described in the following references:United States Patent Application Publication No. US 2011/0277947,entitled “Cellulose Nanofilaments and Method to Produce Same”, of Hua etal.; United States Patent Application Publication No. US 2014/0083634,entitled “Method and an Apparatus for Producing Nanocellulose”, ofBjoerkqvist et al.; and United States Patent Application Publication No.US 2014/0284407, entitled “A Method for Producing NanofibrillarCellulose”, of Tamper et al.

The fiber morphology influences the amount of energy required todisintegrate it into NFC. Delamination can be facilitated by weakeningfiber cell walls or decreasing the strength of fiber-to-fiber bondsthrough enzymatic or oxidative pretreatments as noted above.Pretreatments can be targeted to certain regions of the fiber or cause ageneral weakening effect. For example, cellulase enzymes degrade theamorphous portion of the fiber, whereas the TEMPO oxidation weakens theentire surface of the fiber by decreasing the degree of polymerizationof cellulose. The TEMPO pretreatment weakens the fiber indiscriminatelyby converting primary hydroxyl groups of polysaccharides to carboxylgroups. The same techniques can also be used after mechanicalfibrillation to achieve a desired quality of NFC. The choice and extentof pretreatment, as well as the morphology of the starting material,will influence the morphology of the nanofibrillated cellulose produced.For example, pulps that undergo extensive enzymatic hydrolysis beforedisintegration tend to be more uniform in size with a higher degree ofcrystallinity. With a lower fraction of amorphous cellulose, thesefibers look more like cellulose nanocrystals and have a lower specificsurface area. Mechanical disintegration with a microgrinder willincrease the surface area of the fibrils and cause more branching. Forglue reinforcement applications, this is a desired outcome as greatersurface area will increase the amount of interfacial bonding with thematrix glue, PVOH.

Further details concerning making NFC or MFC with peroxide or ozone areseen in U.S. Pat. No. 7,700,764 to Heijnesson-Hulten, entitled Method ofPreparing Microfibrillar Polysaccharide (Akzo Nobel N.V.); United StatesPatent Application Publication No. US 2015/0167243 of Bilodeau et al.,entitled Energy Efficient Process for Preparing Nanocellulose Fibers(University of Main System Board of Trustees); and U.S. Pat. No.8,747,612 to Heiskanen et al., entitled Process for the Production ofMicrofibrillated Cellulose in an Extruder and Microfibrillated CelluloseProduced According to the Process (Stora Enso OYJ). Discussion relatingto making NFC or MFC with N-oxyl compounds is seen in U.S. Pat. No.8,992,728 to Isogai et al., entitled Cellulose Nanofiber, ProductionMethod of Same and Cellulose Nanofiber Dispersion (University of Tokyo);U.S. Pat. No. 8,377,563 to Miyawaki et al., entitled PapermakingAdditive and Paper Containing the Same (Nippon Paper Industries Co.,Ltd.); and U.S. Pat. No. 8,287,692 to Miyawaki et al., entitledProcesses for Producing Cellulose Nanofibers (Nippon Paper IndustriesCo., Ltd.) which discloses a process for making nanofibers using N-oxylcompounds (TEMPO). References for making NFC or MFC with enzymes includeU.S. Pat. No. 8,778,134 to Vehvilainen et al., entitled Process forProducing Microfibrillated Cellulose (Stora Enso OYJ); U.S. Pat. No.8,728,273 to Heiskanen et al., entitled Process for the Production of aComposition Comprising Fibrillated Cellulose and a Composition (StoraEnso OYJ); U.S. Pat. No. 8,647,468 to Heiskanen et al., entitled Processfor Producing Microfibrillated Cellulose (Stora Enso OYJ) which proposestwo enzymatic treatments of the pulp used to make microfibers; and U.S.Pat. No. 8,546,558 to Ankerfors et al., entitled Method for theManufacture of Microfibrillated Cellulose (STFI-Packforsk AB) which alsorelates to the use of an enzyme treatment.

NFC may be obtained through the University of Maine; see “The Universityof Maine—The Process Development Center-Nanofiber R & D,” [Online].Available: http://umaine.edu/pdc/nanofiber-r-d/. [Accessed 24 Nov.2014]. This source is referred to as NFC I in the text and Figures. NFCmay also be obtained from Paperlogic, operator of the first UScommercial nanocellulose plant at the former Southworth Paper and nowPaperlogic mill in Turners Falls, Mass. This source is referred to asNFC II in the text and Figures.

NFC structure is shown in the electron microscope images of FIGS. 11Aand 11B.

Viscosity Analysis of NFC

Aqueous NFC suspensions were prepared to obtain 1% consistency. Thesuspensions were then characterized for their viscosity profiles usingthe test method and apparatus described above. Results appear in Table6.

TABLE 6 NFC Viscosity Profiles NFC I NFC I NFC II NFC II Shear rate, 1/sViscosity, cP Shear rate, 1/s Viscosity, cP 0.50 523000 0.50 47567 0.79366000 0.79 30257 1.26 237000 1.26 20859 1.99 144000 1.99 18659 3.15108000 3.15 20987 5.00 80400 5.00 33392 7.92 93300 7.92 50742 12.6054100 12.56 51553 19.90 72000 19.90 53050 31.50 53200 31.55 46992 50.0021900 50.00 17078 79.20 14100 79.24 9200 126.00 5670 125.59 9716 199.002640 199.05 5741 315.00 1190 315.48 3053 500.00 553 500.00 1381 792.00234 792.44 674 1260.00 100 1255.94 308 1990.00 45.8 1990.54 124 2000.0030.8 2000.00 111

The data from Table 6 is shown graphically in FIG. 12. It is appreciatedfrom FIG. 12 that NFC is a pseudoplastic material and the properties ofNFC I and NFC II are substantially identical.

NFC Breaking Length and Stretch

100% NFC films or handsheets were formed by vacuum filtration usingnylon membrane with 0.45 μm pore size utilizing the NFC I and NFC IImaterials. Fully restrained drying of NFC films was conducted byattachment of one side of the film to a metal plate and the other sidewas pressed by a customized perforated ring with a piece of heavy metalon top. The diameter of dried NFC films was 1.5 in. Each film was cutinto a 15 mm×1 in strip for tensile testing which provided theinformation to calculate the breaking length and maximum stretch atbreak. Results appear in Table 7, as well as in FIGS. 13 and 14.

TABLE 7 NFC Properties Breaking Max Sample length, km stretch, % NFC I6.9 7.5 NFC II 6.3 11.4

Viscosity Modifiers

As will be appreciated from the foregoing, NFC has a very high viscosityeven at 1% consistency. This is due to the large surface area andhydrogen bonds between the nano fibrils. The NFC slurry tends toagglomerate and form uneven spots. Such viscous slurry is not generallysuitable to use directly as a bonding agent due to transfer issues tothe sheet. A viscosity modifier is needed to evenly disperse the NFCparticles and substantially reduce its viscosity with the increase ofshear rate. Ideally, the agglomerated nano cellulose fibrils areseparated from each other and a new interface, between an inner surfaceof the liquid dispersion medium and the surface of the particles to bedispersed, is generated. A medium to disperse NFC is expected to havehigh viscosity, but not necessarily to be the same as the viscosity ofNFC. Mixing the viscosity modifier and NFC slurry will have asynergistic effect to suspend NFC. Since NFC slurry has a shear-thinningproperty, the viscosity modifier is expected to have consistentproperties to prevent phase separation. Preferred viscosity modifiersinclude xanthan gum, carboxymethylcellulose (CMC) and to a lesser extentpectin.

Xanthan gum is a nature-derived, high-molecular weight polysaccharideproduced by the microorganism Xanthomonas campestris through microbialfermentation having the structure shown below. Xanthan gum, sometimesreferred to herein as “XG”, is highly versatile in personal careapplications as it is resistant to enzymatic degradation, extremelystable over a wide range of temperatures and pH. Xanthan gum isprimarily used as a thickener, but is also a stabilizer for suspensions,emulsions, foams and solid particles in water-based formulations. Thexanthan gum used in this study was purchased from Sigma-Aldrich (Xanthangum from Xanthomonas campestris, G1253-500G).

Typically, xanthan gum's molecular weight distribution ranges from 2×10⁶to 20×10⁶ Da (1 Da=1 g/mol). This molecular weight distribution dependson the association between chains, forming aggregates of severalindividual chains. The variations of the fermentation conditions used inproduction are factors that can influence the molecular weight ofxanthan gum. See Garcia-Ochoa, F., et al. (2000), “Xanthan gumproduction, recovery, and properties.” Biotechnology Advances 18:549-579.

A suitable carboxymethylcellulose is CMC-7MT which is a technical gradeof sodium carboxymethyl cellulose manufactured by Hercules. It has adegree of substitution of about 0.7, a polymerization degree of 1000,and a molecular weight of 250,000 g/mol.

Pectin, sometimes referred to as poly-D-galacturonic acid methyl ester,is available from Sigma-Aldrich (Pectin from Apple, 76282). Itsmolecular weight is 30,000 to 100,000 g/mol.

In addition to xanthan gum and CMC and Pectin, other suitable viscositymodifiers may include other polysaccharides (starches, vegetable gums),other natural gums or proteins such as collagen, furcellaran, gelatinand various synthetic polymers depending on solids content of thecomposition and ratio of NFC/viscosity modifier. Noted are the followingviscosity modifiers which may be employed:

-   -   methylcellulose, ethylcellulose, hydroxyethylcellulose, carboxy        ethylcellulose, natural resins, natural rosins, and the like;    -   starches including corn starch; potato starch; arrowroot; and        the like;    -   ethoxylated linear alcohols;    -   polyethylene glycols, polypropylene glycols, and the like;    -   Natural gums obtained from seaweeds such as Agar, Alginic acid        and Sodium alginate, Carrageenan;    -   Natural gums obtained from non-marine botanical resources such        as Gum arabic from the sap of Acacia trees, Gum ghatti from the        sap of Anogeissus trees, Gum tragacanth from the sap of        Astragalus shrubs, Karaya gum from the sap of Sterculia trees,        Guar gum from guar beans, Locust bean gum from the seeds of the        carob tree, Beta-glucan from oat or barley bran, Chicle gum (an        older base for chewing gum obtained from the chicle tree),        Dammar gum from the sap of Dipterocarpaceae trees, Glucomannan        from the konjac plant, Mastic gum (a chewing gum from ancient        Greece obtained from the mastic tree), Psyllium seed husks from        the Plantago plant, Spruce gum (a chewing gum of American        Indians obtained from spruce trees), Tara gum from the seeds of        the tara tree;    -   Other Natural gums produced by bacterial fermentation such as        Gellan gum;    -   and any combination of the foregoing.

Surface Tension Modifiers

In embodiments used for converting it is desirable to use a surfacetension modifier so that the adhesive coats applicator and pick-uprolls. PVOH is suitable for this purpose.

PVOH for use in connection with the present invention include thoseobtainable from Sekisui Specialty Chemicals, Houston, Tex. as well asother suppliers and distributors. Commercial polyvinyl alcohol resinsare produced by saponifying polyvinyl acetate and include significantlevels of vinyl acetate repeat units. The degree of hydrolysis (mol %)indicates the mol % alcohol repeat units in the polyvinyl alcohol, withthe remainder being in acetate form. A partially hydrolyzed polyvinylalcohol may be used and dissolved in water that is from about 70 molepercent to about 90 mole percent hydrolyzed, such as from about 84 molepercent to about 89 mole percent hydrolyzed. Partially hydrolyzedpolyvinyl alcohols more rapidly dissolve; however, polyvinyl alcoholsthat are hydrolyzed to a greater extent may be used. For instance,polyvinyl alcohol may also be used in the process that has a percenthydrolysis (mole %) of greater than 90%. In some cases, the polyvinylalcohol may be from about 91% to about 99.31% hydrolyzed. The molecularweight of the polyvinyl alcohol used can also vary. A relatively lowmolecular weight polyvinyl alcohol may be used. For instance, thepolyvinyl alcohol may have a viscosity at 4% solids and at 20° C. ofless than about 10 cps. For instance, the viscosity of the polyvinylalcohol at 4% solids and 20° C. can be from about 3.5 cps to about 4.5cps. In other embodiments, however, higher molecular weight polyvinylalcohols can be used that have a viscosity at 4% solids and at 20° C. ofgreater than about 5 cps, such as up to about 75 cps. Generally,polyvinyl alcohol or PVOH resins consist mostly of hydrolyzed polyvinylacetate repeat units (more than 50 mole %), but may include monomersother than polyvinyl acetate in amounts up to about 10 mole % or so intypical commercial resins. Suitable co-monomers include vinylco-monomers in general and especially those with carboxylate orsulfonate functionality as is seen in U.S. Pat. No. 7,642,226. Typicalcommercial polyvinyl alcohols are listed in Table 8, below.Characteristic PVOH Viscosity is measured at 4 wt % solution of thepolyvinyl alcohol in water at a temperature of 20° C. Viscosity isexpressed in centipoises unless otherwise indicated, abbreviated cps orcP.

TABLE 8 Commercial Polyvinyl Alcohol for Adhesive % Viscosity,Volatiles, % Ash, Grade Hydrolysis, cps¹ pH Max. % Max. Super HydrolyzedSelvol 125 99.3+ 28-32 5.5-7.5 5 1.2 Selvol 165 99.3+ 62-72 5.5-7.5 51.2 Fully Hydrolyzed Selvol 103 98.0-98.8 3.5-4.5 5.0-7.0 5 1.2 Selvol107 98.0-98.8 5.5-6.6 5.0-7.0 5 1.2 Selvol 310 98.0-98.8  9.0-11.05.0-7.0 5 1.2 Selvol 325 98.0-98.8 28.0-32.0 5.0-7.0 5 1.2 Selvol 35098.0-98.8 62-72 5.0-7.0 5 1.2 Intermediate Hydrolyzed Selvol 41891.0-93.0 14.5-19.5 4.5-7.0 5 0.9 Selvol 425 95.5-96.5 27-31 4.5-6.5 50.9 Partially Hydrolyzed Selvol 502 87.0-89.0 3.0-3.7 4.5-6.5 5 0.9Selvol 203 87.0-89.0 3.5-4.5 4.5-6.5 5 0.9 Selvol 205 87.0-89.0 5.2-6.24.5-6.5 5 0.7 Selvol 513 86.0-89.0 13-15 4.5-6.5 5 0.7 Selvol 52387.0-89.0 23-27 4.0-6.0 5 0.5 Selvol 540 87.0-89.0 45-55 4.0-6.0 5 0.5¹4% aqueous solution, 20° C.Commercial formulations containing PVOH are available from a variety ofsources including H.B. Fuller of Minnesota. Such compositions maycontain optional additives if so desired. See U.S. Pat. No. 7,201,815.

It was observed that the NFC/Xanthan Gum bonding agent had difficultycoating a rubber pickup roll in the converting apparatus. A poor pickupof the bonding agent resulted in no lamination between the two-plybasesheet. For good wetting to occur, the surface energy of the adhesiveshould be less than the surface energy for the substrate to which it isapplied. A surface tension analysis was conducted using a SITA pro linet15 tensiometer to verify this concern. As shown in FIG. 15A, at theroom temperature, tap water has a surface tension of 72 mN/m. Adding0.1% xanthan gum into water did not change the surface tensionsignificantly. Mixing 0.5% NFC into the tap water slightly increased thesurface tension to 73 mN/m. However, when the 0.5% NFC and 0.1% xanthangum were mixed together, the surface tension increased to 93 mN/m. Thisdramatic change is additional evidence to indicate that the xanthan gumimproved the NFC suspension and distribution in aqueous solution.

As a comparison (FIG. 15B), the surface tension of regular PVOH glue (2%PVOH) was below 50 mN/m after 0.6 sec, significantly less than water.The difference in surface tension between the NFC bonding agent and PVOHexplained the challenge of coating NFC bonding agent on the rubber roll.It appeared necessary to lower the surface tension of the NFC bondingagent to a certain extent. By adding 2% PVOH into the NFC bonding agent,the surface tension of CH1 (2% PVOH+0.5% NFC) and CH2 (2% PVOH+0.5%NFC+0.1% xanthan gum) were effectively reduced, and the current surfacetension did not cause issues during the pilot trial. It needs to benoted that the purpose of adding PVOH was only for reducing surfacetension. 2% PVOH itself is too weak to form a good plybond.

In FIGS. 15A and 15B the dynamic surface tension of NFC bonding agentalong with other liquid is measured at room temperature, using a SITApro line t15 tensiometer. The device is based on the bubble pressuremethod whereby air is pumped through a capillary into the to-be-analyzedliquid. According to the Young-Laplace equation, the pressuredifference, P_(max)−P_(min), seen within the bubble's lifetime isproportional to the surface tension.

The sample temperature is equilibrated to room temperature beforetesting. The capillary of the tensiometer is sunk vertically into theliquid to be measured until the liquid is within the grey marking on thetemperature sensor. “Auto mode” was used to measure the dynamic surfacetension in the range of bubble lifetimes. For comparison purposesthroughout the specification and claims, a surface tension of testedsample at bubble life time 5 seconds is used to characterize materials.

As a result of their adsorption at the surface or interface, surfacetension modifiers bring about a reduction in the dynamic surfacetension. Immediately after the surface is produced, the dynamic surfacetension has the same value as the pure liquid. The value then reducesuntil an equilibrium value is reached. The time required for thisdepends on the diffusion rate and the adsorption rate of the surfacetension modifier. Interfaces are produced extremely quickly in processessuch as spraying, foaming, cleaning, printing, emulsifying or coating.In such processes it is not just the equilibrium value of the surfacetension that is the decisive influence, but also the kinetics of theinterface formation. The molecular mobility of the surface tensionmodifier used becomes an important factor in the formation of thedynamic surface tension. In this application, an ideal surface tensionmodifier is expected to effectively reduce the surface tension of NFCbonding agent within a few seconds of bubble lifetime.

Additional surface tension modifiers include surfactants in general suchas anionic surfactants, cationic surfactants, zwitterionic surfactantsand more preferably nonionic surfactants. One preferred nonionicsurfactant is Tergitol® MIN FOAM 1× available from Sigma-Aldrich. Thismaterial is a polyglycol ether nonionic surfactant of the formula:

where m and n are integers.

Other suitable surface tension modifiers include C₁₂-C₁₈-alkylpolyethylene glycol-polypropylene glycol ethers having in each case upto 8 mol of ethylene oxide and propylene oxide units in the molecule. Itis also possible to use other known surfactants, for exampleC₁₂-C₁₈-alkyl polyethylene glycol-polybutylene glycol ethers having ineach case up to 8 mol of ethylene oxide and butylene oxide units in themolecule, end group-capped alkyl polyalkylene glycol mixed ethers, orC₈-C₁₄-alkyl polyglucosides with a degree of polymerization of about 1to 4 and/or C₁₂-C₁₈-alkyl polyethylene glycols with 3 to 8 ethyleneoxide units in the molecule. Likewise suitable are surfactants from thefamily of the glucamides, for example alkyl N-methylglucamides in whichthe alkyl moiety preferably originates from a fatty alcohol with thecarbon chain length C₆-C₁₄. It is advantageous in some cases when thesurfactants described are used as mixtures, for example the combinationof alkyl polyglycoside with fatty alcohol ethoxylates or of glucamidewith alkyl polyglycosides. The presence of amine oxides, betanes andethoxylated alkylamines is also possible.

Antimicrobial Agents

The ply-bonding compositions of the invention suitably includeantimicrobial agents, most preferably food-grade preservatives whichfunction as antibacterial agents and antifungal agents. Without theaddition of antimicrobial agent, all the NFC-xanthan gum laminatingagents became moldy after two weeks at room temperature in a sealedcentrifuge tube. The addition of a trace amount of potassium sorbate wasfound effective to inhibit the growth of microorganism in NFC laminatingagent. Potassium sorbate is the potassium salt of sorbic acid. It is awhite salt that is very soluble in water and is primarily used as a foodpreservative. Sorbate is a lipophilic compound and may permeate thebilipid layer of the bacterial cytoplasmic membrane. Interaction ofsorbate with that membrane may result in the interference ofmembrane-associated cellular functions that inhibit the growth ofmicrobes. The typical culinary usage rates of potassium sorbate are0.025% to 0.1%. A light dosage of 0.025% potassium sorbate was addedinto 0.5% and 1% NFC-0.1% xanthan gum laminating agent. No mold has beenfound in the laminating agent after storing at room temperature for twomonths. Considering paper towel is a food contact material, potassiumsorbate is a preferred antiseptic for use in NFC laminating agent of thepresent invention.

Other preferred antimicrobial agents may include other food-gradepreservative compositions which include sorbic acid, sodium sorbate,calcium sorbate, benzoic acid, calcium benzoate, potassium benzoate,sodium benzoate, calcium hydrogen sulphite, calcium sulphite, potassiumbisulphite, potassium metabisulphite, potassium sulphite, sodiumbisulphite, sodium metabisulphite, sodium sulphite, sulphur dioxide,potassium nitrate, potassium nitrite, sodium nitrate, sodium nitrite,calcium propionate, potassium propionate, propionic acid, sodiumpropionate, mixtures thereof and the like.

Tackifiers

Tackifiers suitable for use in conjunction with the adhesivecompositions described herein may, in some embodiments, include, but arenot limited to, methylcellulose, ethylcellulose, hydroxyethylcellulose,carboxy methylcellulose, carboxy ethylcellulose, amides, diamines,polyesters, polycarbonates, silyl-modified polyamide compounds,polycarbamates, urethanes, natural resins, natural rosins, rosin estersSYLVATAC®RE85 and SYLVALITE® RE100, both esters of tall oil rosin,available from Arizona Chemical, shellacs, acrylic acid polymers,2-ethylhexylacrylate, acrylic acid ester polymers, acrylic acidderivative polymers, acrylic acid homopolymers, anacrylic acid esterhomopolymers, poly(methyl acrylate), poly(butyl acrylate),poly(2-ethylhexyl acrylate), acrylic acid ester co-polymers, methacrylicacid derivative polymers, methacrylic acid homopolymers, methacrylicacid ester homopolymers, poly(methyl methacrylate), poly(butylmethacrylate), poly(2-ethylhexyl methacrylate),acrylamido-methyl-propane sulfonate polymers, acrylamido-methyl-propanesulfonate derivative polymers, acrylamido-methyl-propane sulfonateco-polymers, acrylic acid/acrylamido-methyl-propane sulfonateco-polymers, benzyl coco di-(hydroxyethyl) quaternary amines,p-T-amyl-phenols condensed with formaldehyde, dialkyl aminoalkyl(meth)acrylates, acrylamides, N-(dialkyl amino alkyl) acrylamide,methacrylamides, hydroxy alkyl(meth)acrylates, methacrylic acids,acrylic acids, hydroxyethyl acrylates, ethylene vinyl acetate, vinylacetate ethylene polymers, aliphatic hydrocarbons, cycloaliphatichydrocarbons (e.g., EASTOTAC® products, available from Eastman ChemicalCo.), aromatic hydrocarbons, aromatically modified aliphatichydrocarbons, cycloaliphatic hydrocarbons, hydrogenated versions of theforegoing hydrocarbons, terpenes, polyterpenes, modified terpenes (e.g.,phenolic modified terpene resins like SYLVARES™ TP96 and SYLVARES™TP2040, available from Arizona Chemical, and the like, any derivativethereof, and any combination thereof.

PVOH may also be used as a tackifier as well as a surface tensionmodifier.

In some embodiments, tackifiers suitable for use in conjunction with theadhesive compositions described herein may be food-grade tackifiers.Examples of food-grade tackifiers include, but are not limited to,methylcellulose, ethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, carboxy ethylcellulose, natural resins, natural rosins,and the like, and any combination thereof.

Water Soluble Cellulose Derivatives and Water Soluble Polyols

The invention compositions may include water soluble cellulosederivatives and/or water soluble polyols as hereinafter described inmore detail. Water soluble cellulose derivatives include celluloseethers, hydroxyethyl cellulose, carboxymethylcellulose, carboxymethylhydroxyethyl cellulose and the like. “Water soluble polyols” includewater soluble monomeric polyol, water soluble polymeric polyol,especially including PEG, glycols in general, functionalized polymericpolyol and combinations thereof. In some cases, when we refer to watersoluble polyols, we refer to polyols other than PVOH.

Additional Components

A typical adhesive composition may optionally include additionaladditives. Additives suitable for use in conjunction with the adhesivecompositions described herein may include, but are not limited to,crosslinkers, insolubilizers, fillers, thickeners, water-resistanceadditives, flame retardants, lubricants, softening agents, pigments,dyes, antioxidants, UV-stabilizers, resins, rosins, waxes, flowingagents, compatibilizers, aromas, and the like, and any combinationthereof. Various exemplary additives are seen in United States PatentApplication Publication No. US2015/0090156 of Combs et al., noted above.

NFC/PVOH Adhesive Formulation

Compositions with relatively high PVOH content and relatively low NFCcontent may be formulated from commercial polyvinyl alcohol (PVOH)adhesive and NFC by diluting a commercially available 8% solids byweight aqueous PVOH adhesive and thoroughly mixing with NFC as detailedin Table 9, wherein it is seen Conventional PVOH glue was diluted to4-6% solid content from commercial PVOH plybond water-based adhesive(WB2746, H.B. Fuller, 8% solids). Two types of NFC were employed in theformulations of Table 9: NFC A, a relatively fine grade in an aqueousdispersion, 3.28% by weight solids; NFC B, a somewhat coarser grade inan aqueous dispersion, 1.92% solids; were mixed with the commercial PVOHto prepare NFC reinforced PVOH glues having the composition shown inTable 9.

TABLE 9 Preparation of Glue PVOH 1.92% Solids, % 8% 3.28% NFC B, Glue #Sample (w/w) PVOH, g NFC A, g g Water, g Total, g 1 PVOH 4 150 150.00300.00 2 4.5 170 132.22 302.22 3 5 190 114.00 304.00 4 5.5 210 95.45305.45 5 6 225 75.00 300.00 6 PVOH + 5% NFC A * 4 150 18.29 131.71300.00 7 4.5 170 20.73 111.49 302.22 8 5 190 23.17 90.83 304.00 9 5.5210 25.61 69.84 305.45 10 6 225 27.44 47.56 300.00 11 PVOH + 5% NFC B *4 150 31.25 118.75 300.00 12 4.5 170 35.42 96.81 302.22 13 5 190 39.5874.42 304.00 14 5.5 210 43.75 51.70 305.45 15 6 225 46.88 28.13 300.00 *based on PVOH content

PVOH Based Adhesive Viscosity Characteristics

The above and additional glues with different levels of PVOH and NFCwere tested for their viscosity with respect to shear rate using theprocedure noted above. The viscosity of each glue represented ascentiPoise vs. shear rate (γ, which is proportional to rotor speed andinversely related to gap) is shown in FIGS. 16 and 17. All the PVOHglues without NFC were typical Newtonian fluids in which viscosity staysthe same regardless of shear rate in the range of 0.5-2000 s⁻¹.Viscosity of 4.5% PVOH was over three times the viscosity of 3% PVOH.All the glues that contain 5% NFC based on the dry weight of PVOHdisplayed a shear thinning property. For the NFC reinforced glues, 3%PVOH+5% NFC and 4.5% PVOH+5% NFC, the incorporation of NFC significantlyincreased the viscosity of the glue and the degree of increase dependson the shear rate. Two glue samples, 3% PVOH and 2.5% PVOH+5% NFC, hadvery similar viscosity curves. Therefore, it is likely that a similarvolume of glue will be applied on base web when using these two types ofglue. However, 2.5% PVOH+5% NFC provides a benefit in terms of softnesssince less total PVOH is used.

FIGS. 16, 17 likewise show that standard PVOH glue is converted from aNewtonian fluid to a pseudoplastic (shear-thinning) fluid by addition ofa small quantity of NFC. Low-shear viscosity is also significantlyincreased. Glue containing 2.5% PVOH with NFC has a viscosity in asimilar range as 3% PVOH. If the fluid dynamics of each glue results inthe transfer of a similar liquid volume, it is reasonable to assume thatthe NFC glue supplied about 20% less PVOH (2.5/3). Softness is improveddue to the smaller amount of glue being less detectable to touch. Theglue/tissue interface between the applicator roll and emboss roll mayinvolve the most important transfer of glue, and the shear rate becomesan important consideration for non-Newtonian fluids. If the shear rateis low, the alternative glues will have higher viscosity than 3% PVOH.If the shear rate is above about 10 sec⁻¹, the alternative glues will bethinner. Given that the roll speeds are matched and the nip pressure islow, the shear rate is expected to be low. Thus, the alternative gluesare hypothesized to act as higher viscosity glues in terms of wet tackwhile delivering a smaller quantity of dry residual.

NFC Adhesive Viscosity Characteristics

Suitable bonding agents based on NFC and viscosity modifiers andoptionally other components are prepared in dilute aqueous solution orsuspension by mixing under shear, typically with an NFC content of 1% byweight or so with viscosity modifier and other optional components.Representative aqueous compositions are enumerated in Table 10 whereinthe composition component content is reported in % by weight of thetotal composition, of which the balance is water (98%+) in most cases.When the adhesive is also intended for use in converting operations withan applicator roll, especially a rubber roll, a surface tension modifieris included as noted above. The data is tabulated in Table 10 and shownFIGS. 18-21.

The data shown in FIGS. 18-21 is tabulated below in Table 10.

TABLE 10 Viscosity Properties 0.5% NFC + 0.1% Xanthan 0.5% NFC + 0.07%Xanthan 0.75% NFC + 0.1% Xanthan 1.0% NFC + 0.1% Xanthan 1.0% NFC +0.13% Xanthan Gum Gum Gum Gum Gum Shear rate Viscosity Shear rateViscosity Shear rate Viscosity Shear rate Viscosity Shear rate Viscosity1/s cP 1/s cP 1/s cP 1/s cP 1/s cP 0.50 2285.51 0.50 1972.57 0.504224.78 0.50 7165.04 0.50 7934.89 0.79 1575.43 0.79 1309.78 0.79 2820.210.79 4966.77 0.79 5316.51 1.26 1043.28 1.26 874.30 1.26 1869.05 1.263322.62 1.26 3582.18 1.99 704.23 1.99 587.04 1.99 1227.38 1.99 2235.631.99 2426.69 3.15 478.15 3.15 405.18 3.15 801.51 3.15 1504.34 3.151666.15 5.00 333.09 5.00 285.76 5.00 568.07 5.00 1032.28 5.00 1232.167.92 205.50 7.92 205.12 7.92 427.17 7.92 713.33 7.92 856.73 12.56 139.3512.56 156.35 12.56 293.15 12.56 508.80 12.56 581.95 19.91 112.90 19.91263.69 19.91 216.41 19.91 395.89 19.91 414.02 31.55 77.61 31.55 315.8931.55 149.16 31.55 381.45 31.55 303.68 50.00 56.27 50.00 857.91 50.00101.08 50.00 273.30 50.00 171.76 79.24 40.55 79.25 484.10 79.24 79.2379.24 273.26 79.24 132.78 125.59 27.96 125.59 251.89 125.59 62.87 125.59248.12 125.59 97.72 199.05 23.66 199.06 126.79 199.05 74.96 199.05139.44 199.05 75.55 315.48 19.10 315.478 68.06 315.48 65.16 315.48 94.73315.48 53.36 500.00 15.07 500.00 42.41 500.00 38.42 500.00 51.36 500.0035.85 792.45 11.95 792.45 26.29 792.45 25.76 792.45 35.80 792.45 26.271255.95 8.89 1255.94 17.51 1255.94 23.22 1255.94 25.75 1255.94 20.361990.54 7.37 1990.53 12.09 1990.54 15.91 1990.54 18.91 1990.53 16.712000.00 7.36 2000.00 12.17 2000.00 15.62 2000.00 16.52 2000.00 16.881.0% NFC Slurry_Paperlogic 1.0% Xanthan Gum 5% PVOH_TT3005 2.5%PVOH_TT3005 4.5% PVOH Shear rate Viscosity Shear rate Viscosity Shearrate Viscosity Shear rate Viscosity Shear rate Viscosity 1/s cP 1/s cP1/s cP 1/s cP 1/s cP 0.50 47567.1 0.50 16684 0.50 61.04 0.50 6.44 0.5038.43 0.79 30257 0.79 12759.8 0.79 58.83 0.79 7.00 0.79 41.30 1.2620858.7 1.26 8829.06 1.26 59.01 1.26 7.28 1.26 42.02 1.99 18659.4 1.995897.01 1.99 60.85 1.99 7.03 1.99 40.17 3.15 20986.7 3.15 3868.86 3.1560.30 3.15 7.10 3.15 40.83 4.50 33391.9 4.50 2501.74 5.00 60.71 5.007.03 5.00 40.68 7.92 50741.6 7.92 1609.89 7.92 60.86 7.92 7.04 7.9240.82 12.56 51552.9 12.56 1040.07 12.56 60.96 12.56 7.06 12.56 40.9919.90 53049.5 19.91 676.49 19.91 61.12 19.91 7.07 19.91 41.08 31.5546991.5 31.55 441.97 31.55 61.23 31.55 7.09 31.55 41.18 50.00 17077.7 50292.58 50 61.24 50 7.09 50 41.22 79.24 9200.18 79.24 195.90 79.24 61.0879.24 7.08 79.24 41.21 125.59 9716.41 125.59 132.61 125.59 60.58 125.597.06 125.59 41.12 199.05 5740.54 199.05 91.19 199.05 59.95 199.05 7.06199.05 40.95 315.48 3052.84 315.48 63.50 315.48 59.41 315.48 7.07 315.4840.76 500.00 1381.11 500 45.08 500 58.94 500.00 7.08 500 40.66 792.44673.67 792.446 32.49 792.45 58.37 792.45 7.15 792.45 40.51 1255.94307.66 1255.94 23.91 1255.94 57.48 1255.94 7.40 1255.94 40.15 1990.54123.97 1990.54 18.13 1990.54 55.82 1990.54 8.04 1990.54 39.46 2000111.17 2000 18.04 2000 56.04 2000 8.04 2000 39.64 0.5% NFC + 0.1% CMC 1%NFC + 0.1% CMC 1% CMC 0.5% NFC + 0.1% Pectin 1% NFC + 0.1% Pectin Shearrate Viscosity Shear rate Viscosity Shear rate Viscosity Shear rateViscosity Shear rate Viscosity 1/s cP 1/s cP 1/s cP 1/s cP 1/s cP 0.501448.19 0.50 6509.86 0.50 29.58 0.50 2448.86 0.50 14498.6 0.79 1085.570.79 4470.14 0.79 9.71 0.79 1736.49 0.79 9780.89 1.26 792.46 1.263164.83 1.26 5.53 1.26 1344.6 1.26 6842.66 1.99 507.88 1.99 2331.13 1.993.54 1.99 1524.33 1.99 5595.46 3.15 325.95 3.15 1852.03 3.15 3.08 3.151849.64 3.15 5920.71 5.00 218.70 5 1369.12 5.00 2.75 5.00 1805.29 5.006035.95 7.92 146.73 7.92 1028.99 7.92 2.59 7.92 1992.44 7.92 5883.8312.56 105.28 12.56 764.01 12.56 2.47 12.56 2233.02 12.56 6096.8 19.979.38 19.91 625.82 19.91 2.39 19.91 2835.81 19.91 8231.61 31.55 61.1431.55 525.88 31.55 2.34 31.55 3109.2 31.55 10798.3 50 49.79 50 523.52 502.30 50.00 2201.81 50.00 10238.7 79.24 41.42 79.25 202.46 79.24 2.2679.24 1381.82 79.25 3706.51 125.59 35.14 125.59 86.02 125.59 2.24 125.601339.05 125.60 541.87 199.05 28.87 199.05 54.57 199.05 2.23 199.061394.46 199.05 50.96 315.48 21.84 315.48 43.02 315.48 2.26 315.48 514.42315.48 43.13 500.00 18.31 500 33.78 500 2.38 500.00 208.01 500.00 29.51792.45 16.67 792.45 28.15 792.45 2.61 792.45 101.96 792.45 27.03 1255.9412.95 1255.94 23.89 1255.94 3.04 1255.94 47.02 1255.94 26.63 1990.549.58 1990.54 18.98 1990.54 3.69 1990.53 24.64 1990.53 16.57 2000 9.552000 18.80 2000 3.70 2000 23.02 2000 18.42 1% Pectin 2.5% PVOH_TT30054.5% PVOH 1.0% NFC Slurry_Paperlogic Shear rate Viscosity Shear rateViscosity Shear rate Viscosity Shear rate Viscosity 1/s cP 1/s cP 1/s cP1/s cP 0.50 40.39 0.50 6.44 0.50 38.43 0.50 47567.1 0.79 39.15 0.79 7.000.79 41.30 0.79 30257 1.26 38.07 1.26 7.28 1.26 42.02 1.26 20858.7 1.9936.15 1.99 7.03 1.99 40.17 1.99 18659.4 3.15 33.87 3.15 7.10 3.15 40.833.15 20986.7 5.00 33.00 5.00 7.03 5.00 40.68 5.00 33391.9 7.92 32.387.921 7.04 7.92 40.82 7.92 50741.6 12.56 31.83 12.56 7.06 12.56 40.9912.56 51552.9 19.91 31.27 19.91 7.07 19.91 41.08 19.90 53049.5 31.5530.79 31.55 7.09 31.55 41.18 31.55 46991.5 50 30.36 50 7.09 50 41.2250.00 17077.7 79.24 29.90 79.24 7.08 79.24 41.21 79.24 9200.18 125.5929.41 125.59 7.06 125.59 41.12 125.59 9716.41 199.05 28.80 199.05 7.06199.05 40.95 199.05 5740.54 315.48 27.93 315.48 7.07 315.48 40.76 315.483052.84 500 26.81 500.00 7.08 500 40.66 500.00 1381.11 792.45 25.35792.45 7.15 792.4 40.51 792.44 673.67 1255.94 23.54 1255.94 7.40 1255.9440.15 1255.94 307.66 1990.54 21.50 1990.54 8.04 1990.54 39.46 1990.54123.97 2000 21.46 2000 8.04 2000 39.64 2000 111.17

Bonding Agent and Component Viscosity

According to viscosity analysis (FIGS. 18-21), both NFC slurry andxanthan gum are pseudoplastic materials and their viscosities aresignificantly higher than 4.5% PVOH. At the same concentration 1%,xanthan gum has much lower viscosity than NFC. By mixing 0.1% xanthangum with 1% NFC, the viscosity of 1% NFC+0.1% xanthan gum wassignificantly decreased and the viscosity appears very similar to 1%xanthan gum. The blend of 1% NFC with 0.13% xanthan gum completelysmoothens the viscosity curve and makes the viscosity even lower than 1%xanthan gum. This observation suggested that a tiny amount of xanthangum was effective in dispersing and suspending NFC to increase itsfluidity. A similar trend can also be found for 0.5% NFC with aviscosity reducing amount of xanthan gum. At a commercial convertingspeed 1000-2000 fpm, the shear rate range is roughly equivalent tobetween 100 and 2000 s⁻¹, and the viscosity of NFC-xanthan gumlaminating agents is in between 2.5% and 4.5% PVOH, which allows theNFC-xanthan gum laminating agents to run at converting line speed. FIG.18 also provides information to help determine the optimal ratio of NFCto xanthan gum. For example, 0.07% xanthan gum was found enough tosuspend 0.5% NFC. The big jump of viscosity curve beyond 10 s⁻¹ shearrate indicated that the amount of xanthan gum is insufficient toovercome the strong friction of NFC particles at high shear rate, andthe high viscosity is a risk for a stable run of converting andnon-uniform application of laminating agent to the basesheet. Based onthe viscosity information, a recommended ratio of NFC to xanthan gumappears to be in the range of 1:0.13-0.2.

Bonding Agents formulated with CMC and pectin show similar rheologicalbehavior as is seen in FIGS. 20, 21.

Debonder Effect on Lamination

Adding debonder into the basesheet during the papermaking process is acommon way to improve the softness of the finished product. However,having debonder at the air layer of a basesheet can cause difficultiesfor converting basesheet into multi-ply products at normalcommercialization speed (1500-2000 fpm). Robust ply-bonding adhesive ofthe invention addresses this problem without impairing the softness offinished product. By selecting an appropriate recipe of NFC containingply-bonding adhesive, the negative impact of debonder is overcome andsofter towel with stronger plybond results. In the examples whichfollow, it is seen the addition of debonder in the air layer showednegative impact on the Peel Test Plybond. Without intending to be boundby any particular theory, it is believed that the debonder creates aslippery surface at the air side and hinders the lamination of the twoair sides together. The NFC containing ply-bonding adhesive unexpectedlyand effectively improved the Peel Test Plybond of TAD towel whichcontained debonder on the air side. The improvement was up to 70%.Details are discussed below.

Debonder Examples 1-18

A laboratory study was conducted to evaluate the effect of NFCcontaining ply-bonding adhesive lamination on debonder treated TAD towelbasesheet. A debonder made up of 30 wt % of imidazolinium (Im+) quats ina 1:1 mixture of PEG-400-mono and dioleates was sprayed on the air sideof TAD basesheet at 0, 2, and 4 lb/ton individually. Peel Test Plybondwas measured for the control basesheet (no debonder) and debondertreated basesheet laminated using regular plybond adhesive glue (4.5%PVOH) and two types of NFC containing ply-bonding adhesives. It wasfound that the NFC containing ply-bonding adhesives significantlyincreased peel test plybond up to 70% on TAD basesheet with debondertreatment, as compared to the same or less PVOH glue composition withoutany NFC.

The NFC containing ply-bonding adhesive was prepared by mixing plybondadhesive H.B. Fuller TT3005 with NFC slurry (at 3% consistency; producedby Paper Logic Company, Turners Falls, Mass.).

Diluted debonder was sprayed on the air side surface of a 2″×12″ TADtowel basesheet in a well-controlled manner. To determine the dilutionfactor, a preliminary spraying test was conducted using water only. Thedry weight of 2″×12″ TAD towel basesheet was weighed first, and then thewater was sprayed on the air side of the basesheet twice, from left toright and from right to left, to make sure the whole area of the airside was covered by water. After that, the total weight of the wetbasesheet was weighed. The difference between the dry weight and the wetweight was the amount of water that stayed on the basesheet (Table 11).The water spraying test was repeated 10 times and it was found that theCV² was fewer than 5% which means the results were consistent, thereforethis method can be used to spray debonder by diluting debonder to acertain concentration.

For debonder spraying preparation, the debonders were diluted 807 and404 times when applying 2 lb/ton and 4 lb/ton on the basesheet,respectively. Due to the slight difference in physical propertiesbetween diluted debonder and water, 2 to 3 sprays of diluted debonderwas needed on each basesheet. The actual amount of debonder applied wascalculated using the retained weight of the diluted debonder on thebasesheet and the dilution factor. The average applied debonder wasfairly close to 2 lb/ton and 4 lb/ton (see Tables 11 and 12 forcalculation).

TABLE 11 Water Spraying Test Basesheet After 2 (2″ × 12″) Dry wt, gsprays, g Water, g 1 0.375 0.690 0.315 2 0.377 0.680 0.303 3 0.381 0.6970.316 4 0.380 0.702 0.322 5 0.379 0.657 0.278 6 0.374 0.680 0.306 70.378 0.700 0.321 8 0.387 0.676 0.290 9 0.381 0.698 0.316 10  0.3760.668 0.291 Avg 0.379 0.685 0.306 STDEV 0.004 0.015 0.015 CV 1.0% 2.2%4.9%

Calculation of Debonder's Dilution Factor:

2#/ton  debonder = 2#/2000# = 0.1%4#/ton  debonder = 4#/2000# = 0.2%Dilution  factor  for  2#/ton  debonder:x = 0.3058/(0.3788 * 0.1%) = 807Dilution  factor  for  2#/ton  debonder: $\begin{matrix}{x = {0.3058/( {0.3788*0.2\%} )}} \\{= 404}\end{matrix}$

TABLE 12 Debonder Treated Basesheet for 4.5% PVOH + 5% NFC LaminationTarget: 4#/ton debonder Actually 404 times applied Sample After 2-3diluted debonder, (2″ × 12″) Dry wt, g sprays, g debonder, g #/ton 10.3782 0.6692 0.291 3.8 2 0.3837 0.7161 0.3324 4.3 3 0.3889 0.69740.3085 3.9 4 0.3766 0.6935 0.3169 4.2 5 0.3836 0.7524 0.3688 4.8 60.3804 0.7437 0.3633 4.7 Avg 4.3 STDEV 0.398 CV 9%

The laboratory Peel Test Plybond results confirmed that applyingdebonder on the air side of TAD towel had negative impact on theplybond, and using NFC glue could effectively improve the plybond of TADtowel basesheet with debonder treated air side. The addition of NFC isbased on the dry weight of PVOH. The total solids weight of NFCcontaining ply-bonding adhesive was: ADH1 (Glue 1, 4.5% PVOH, 5% NFC):4.5%×(1+5%)=4.7% solids; ADH2 (Glue 2, 4% PVOH, 5% NFC): 4%×(1+5%)=4.2%solids. It is seen in FIG. 22 and Table 13, using 2 lb/ton and 4 lb/tonof debonder decreased the lab peel plybond by 24.2% and 11%,respectively. A higher variation in plybond results was found for 4lb/ton debonder treated specimen. With 2 and 4 lb/ton of debondersprayed on the air side of TAD towel basesheet, compared to the controlglue in each case, NFC glue 1 significantly improved the plybond by 69%and 30%, respectively and NFC glue 2, with less PVOH solids, alsoincreased the plybond by 12%-28%. Compared to the plybond of untreatedbasesheet laminated with control glue 4.5% PVOH, using NFC glue 1 whichhad the same amount of PVOH even increased the plybond of 2 and 4 lb/tondebonder treated basesheet by 28% and 16%.

TABLE 13 Peel Test Plybond 4.5% PVOH 4.5% PVOH 4.5% PVOH ADH1 ADH1 ADH1ADH2 ADH2 ADH2 Control 2#/ton 4#/ton Control 2#/ton 4#/ton Control2#/ton 4#/ton Plybond, Plybond, Plybond, Plybond, Plybond, Plybond,Plybond, Plybond, Plybond, Specimen g g g g g g g g g 1 36.2 28.1 33.348.5 51.1 40.2 32.7 35.4 50.3 2 29.0 28.4 31.2 49.6 43.3 32.0 35.2 31.237.3 3 36.3 28.0 27.9 42.2 42.3 33.5 34.6 30.1 37.0 4 42.4 25.4 27.456.1 47.5 32.2 34.4 37.5 5 39.7 24.0 32.8 48.7 48.2 39.6 29.5 47.0 639.4 35.5 45.8 44.8 56.8 29.4 45.1 Avg 37.2 28.2 33.1 46.8 47.7 43.034.9 31.7 42.4 Stdev 4.6 4.0 6.7 4.0 5.3 9.5 2.9 2.6 5.8 CV 12% 14% 20%8% 11% 22% 8% 8% 14%

Converting

One of the most challenging obstacles of high speed converting is thatthe loss of plybond causes ply separation and eventually stops themachine. Higher web tension along with machine vibration can partiallytear apart the plybond and the faster the converting runs, the moredrastic vibration that the machine will experience. A significantdecrease of plybond, over 40%, was seen with conventional glue when theconverting speed was increased from 1800 fpm to 1900 fpm and above (FIG.24). However, having a robust plybond adhesive, such as ply-bondingadhesive containing NFC, satisfies the need of sustaining a reliableplybond at high converting speed (compare FIGS. 23 and 24).

Moreover, adding debonder into the airside of a basesheet for softnessbenefit will ordinarily decrease the converting speed even more. Forexample, it has been observed that when using debonder treated TADbasesheet and conventional glue, the converting speed was plybondlimited and the speed decreased from 1800 fpm to 1250-1400 fpm. Also inaddition, using NFC containing ply-bonding adhesive might produce asofter product without sacrificing converting speed.

Another factor that affects achievable converting speed is the embosspattern employed. When an arabesque dots emboss pattern was replaced bya new arabesque line emboss pattern (FIG. 25) for better appearance onTAD basesheet, plybond was significantly reduced. The old arabesque dotsemboss pattern was designed for CWP basesheet not for TAD basesheet, andthe emboss clarity was not satisfying when used on TAD sheet. The bondareas of arabesque dots emboss and arabesque line emboss are 5.4% and9.3%, respectively. Although the increase of bond area improves theclarity of emboss, it also requires more conventional glue to laminatethe sheets and as a result, the softness of the finished productdecreased. Plybond also deteriorates with the increase of convertingspeed which could be the limiting factor for a higher production speed(above 1800 fpm).

Converting Trials

The NFC containing ply-bonding adhesive was prepared by mixing controlPVOH glue available from Henkel and H.B. Fuller with NFC slurry (at 3%consistency; produced by Paper Logic Company, Turners Falls, Mass.). Thecontrol glues and NFC containing ply-bonding adhesive included:

-   -   1. Henkel AQUENCE LAM 5137: 5.5% solids    -   2. Henkel bulk tank: 5.5% solids    -   3. Henkel NFC containing ply-bonding adhesive: 5.25% solids        (4.95% PVOH+6% NFC)    -   4. H.B. Fuller TT3000S: 6.0% solids    -   5. H.B. Fuller NFC containing ply-bonding adhesive: 5.5% solids        (5.2% PVOH+5% NFC)

The control glues and NFC containing ply-bonding adhesives were treatedon four (4) different converting lines of the class illustrated anddescribed hereinafter and consistently demonstrated unexpected, superiorresults in terms of runnability, converting speed and plybond. Inparticular, it was found that using NFC containing ply-bonding adhesiveimproves converting productivity by increasing the converting speedwithout decreasing plybond; NFC containing ply-bonding adhesive has apotential application for improved softness; NFC containing ply-bondingadhesive may improve the plybond on debonder-treated basesheet tomaintain the current converting speed while making softer product; andNFC containing ply-bonding adhesive does not have negative impact onsoftness. Still more specifically, at the same converting speed of 1800fpm, H.B. Fuller NFC containing ply-bonding adhesive (5.2% PVOH+5% NFC,total solids 5.5%) improved the plybond by nearly 40% compared to H.B.Fuller glue at 6% solids; at the same plybond target, using Henkel bulktank NFC containing ply-bonding adhesive (4.95% PVOH+6% NFC, 5.25% totalsolids) instead of Henkel bulk tank glue at 5.5% solids enabled theconverting speed increase by 12.5% (from 1600 fpm to 1800 fpm) whilemaintaining the same plybond; and if switching from Henkel Aquence LAM5137 glue to H.B. Fuller NFC containing ply-bonding adhesive, theproductivity could be improved by 30% with reliable plybond (from 1500fpm to 1950 fpm with at least 20 g of plybond).

The converting experiments had results consistent with previous lab andpilot trial observations that, at the same converting speed, NFCcontaining ply-bonding adhesive developed a much stronger bond thanregular glue. In addition, the hypothesis that NFC containingply-bonding adhesive could improve the converting speed was demonstratedby increasing the converting speed from 1600 fpm to 1800 fpm at the sameplybond. A best converting speed of 1950 fpm was achieved with over 20 gof plybond.

In the discussion which follows and on the various Figures, DR refers tothe drive side of a present roll being converted and OP refers to theportion of the roll most distal to the drive side of the present rollbeing converted. Since there is also some variation in plybond along thebeginning, middle and end of the sheet along the longitudinal direction,these features are also identified as beginning, middle or end, asappropriate.

At 1800 fpm converting speed (FIG. 26), the regular glue H.B. FullerTT3000S with 6.0% solids allowed the converting line to run smoothlywith sufficient plybond from 38.7 g at the DR side, 29.8 g at MID and26.7 at the OP side when the paper for converting was from the end of aset of parent rolls. The uneven plybond across the log was due tomechanical settings. Using H.B. Fuller NFC containing ply-bondingadhesive at 5.5% total solids (5.2% PVOH+5% NFC) at the same convertingspeed developed a much stronger plybond which was 46.1 g at the DR side,44.9 at the MID and 39.9 g at the OP side. This result was consistentwith the lab and pilot observation noted above. It is seen that theplybond decreases with the increase of converting speed. The NFCcontaining ply-bonding adhesive improves the plybond at the sameconverting speed, allows the converting run at a higher speed at thesame plybond. FIG. 27 demonstrates this result. Note, also, the resultsseen in Tables 14, 15 and 16, below.

TABLE 14 Plybond Results Plybond Glue Plybond, g H. B. Fuller NFCcontaining ply-bonding 43.6 ± 3.3 adhesive @ 1800 fpm (Est. end) H. B.Fuller TT3000S @ 1800 fpm (End) 31.7 ± 6.3

Henkel PVOH glue has 5.5% solids. Henkel NFC containing ply-bondingadhesive was prepared with Henkel bulk tank glue, and it had 5.25% totalsolids (4.95% PVOH+6% NFC). As shown in FIG. 27, by using Henkel NFCcontaining ply-bonding adhesive, the converting speed was increased to1800 fpm while the plybond was about the same compared to using Henkelbulk tank glue at 1600 fpm. This 12.5% increase of production rate hastremendous commercial value to a converter.

TABLE 15 Plybond Results Plybond Glue Plybond, g Henkel NFC containingply-bonding 23.2 ± 2.5 adhesive @ 1800 fpm (End) Henkel PVOH @ 1600 fpm(End) 22.3 ± 5.1

An even more attractive case is to use H.B. Fuller NFC containingply-bonding adhesive instead of the current Henkel Aquence LAM 5137. Asshown in FIG. 28, H.B. Fuller NFC containing ply-bonding adhesive at5.5% solids (5.2% PVOH+5% NFC) allowed the converting line to run at1950 fpm with plybond of 24.7 g at DR side, 23.2 g at MID and 25.4 g atOP side. The plybond across the log was relatively even and the averageplybond of 24.4 g was very close to the average plybond developed byHenkel bulk tank glue at 1500 fpm. This was a 30% productivityimprovement.

TABLE 16 Plybond Results Plybond Glue Plybond, g Henkel LAM 5137 @ 1500fpm (Middle) 25.9 ± 4.7 H.B. Fuller NFC containing ply-bonding 24.4 ±1.1 adhesive @ 1950 fpm (Middle)

Representative preferred compositions thus may have one or more featuresenumerated in Tables 17 through 24 below and may consist essentially ofthe listed components optionally with ranges adopted from another tablein the series as discussed herein or by omitting a particular featuresuch as wt % of one component or weight ratios of two components. Thevarious ranges in Tables 17 through 23 and 25 through 29 may be combinedor interchanged between compositions as to various ingredients, that is,a general content range as to wt % PVOH content in one table may bematched with a select content range of NFC wt % content in the same oranother table in a particular embodiment of the invention, in which casethe weight ratios listed in the following tables may be inapplicable tothe particular embodiment contemplated as discussed in connection withTables 1A through 1C and Table 2, above.

TABLE 17 Additional PVOH based/NFC Ply- Bonding Adhesive Content RangesComponent Typical Select PVOH (wt %) 2.5%-6%   3%-5% NFC (wt %)0.1%-0.6% 0.125%-0.5% Weight Ratio 0.017-0.24   0.025-0.17 NFC/PVOH NFC 1%-20%   4%-11% (% based on PVOH) Water (wt %) >90% >90% OtherAdditives Balance Balance

Preferred PVOH based/NFC adhesives include those wherein the adhesiveexhibits an Adhesive Viscosity reduction of at least 15% as shear rateis increased from 1 sec⁻¹ to 100 sec⁻¹; more preferably wherein theadhesive exhibits an Adhesive Viscosity reduction of at least 25% asshear rate is increased from 1 sec 100 sec⁻¹; and still more preferablywherein the adhesive exhibits an Adhesive Viscosity reduction of atleast 50% as shear rate is increased from 1 sec⁻¹ to 100 sec⁻¹.

TABLE 18 Additional NFC and PVOH Ply-Bonding Adhesive CompositionContent Ranges Component Typical Select PVOH (wt %) 1%-3%  1.75%-2.5% NFC (wt %) 0.25%-1%     0.4%-0.75% Viscosity modifier   0-0.2%0.05%-0.15% (wt %) NFC 10%-100% 15%-45% (% based on PVOH) Weight Ratio0.08-1    0.15-0.4  NFC/PVOH Weight Ratio 0-15 4-8 NFC/Viscositymodifier Water (wt %) >95% >95% Other Additives Balance Balance

TABLE 19 Additional NFC/Viscosity Modifier Ply-Bonding BondingComposition Content Ranges Component Typical Typical Select NFC (wt %)0.15%-3%  0.175%-2%     0.2%-1.25% Viscosity modifier 0.02%-0.2%0.05%-0.15% 0.07%-0.13% (wt %) Weight Ratio  2.5-10 3-9 4-8NFC:Viscosity Modifier Water (wt %) >95% >95% >95% Other AdditivesBalance Balance Balance

The NFC/Viscosity Modifier Bonding Compositions of Table 19 includethose wherein the ply-bonding agent composition contains a surfacetension modifier. In some embodiments, the ply-bonding adhesive orcomposition has a surface tension of less than 60 mN/m; preferably lessthan 55 mN/m.

TABLE 20 Representative PVOH, Viscosity Modifier Based NFC Ply-BondingAdhesive Compositions Component General Typical PVOH (wt %) 1-5 2-4Viscosity Modifier (wt %) 0.25-3   0.4-2  NFC (wt %) 0.25-1   0.4-0.7PVOH:NFC Weight  1-25  1-10 Ratio Water (wt %) 90-99 95-98 Otheradditives balance balance

TABLE 21 Representative Viscosity Modifier Based Ply-Bonding AdhesiveCompositions Component General Typical Viscosity Modifier (wt %)0.05-2   0.075-1.5  NFC (wt %) 0.05-0.75 0.075-0.65 NFC:ViscosityModifier  2. 5%-1000%   7%-500% Weight Ratio (%) Water (wt %) 95-99  97-98.5 Other additives balance balance

TABLE 22 Representative PVOH/NFC/Viscosity Modifier Ply-Bonding AdhesiveCompositions with NFC:Viscosity Modifier Ratios of <100% ComponentGeneral Typical Viscosity Modifier (wt %) 0.3-2 0.5-1.5 NFC (wt %)0.025-0.2  0.035-0.15  Weight Ratio,  2.5%-75%  3%-15% NFC:ViscosityModifier Ratio (%) PVOH 0.5-5  1-3.5 Water (wt %) >90 >95 Otheradditives balance balance

TABLE 23 Representative NFC Viscosity Modifier Ply-Bonding AdhesiveCompositions with NFC:Viscosity Modifier Ratios of <100% ComponentGeneral Typical Viscosity Modifier (wt %) 0.3-3  0.5-1.5 NFC (wt %)0.05-0.2 0.75-0.15 Weight Ratio,  2.5%-75%  3%-15% NFC:ViscosityModifier Ratio (%) Water (wt %) >90 >95 Other additives balance balance

In Tables 20 through 23, as well as throughout this disclosure,“viscosity modifier” refers to xanthan gum, carboxymethylcellulose,pectin and the like as hereinafter described. Percentages in the aboveTables are based on the weight of the recited component based on theweight of the aqueous composition, except that in Tables 21, 22 and 23and sometimes hereinafter the NFC: modifier ratio in percent is theweight ratio of the two components times 100%, which may be referred toas the percent weight ratio. The chemistries in Tables 21 through 24include relatively low ratios of NFC to viscosity modifier which can beviewed in these types of compositions, i.e. where the amount ofviscosity modifier is greater than the amount of NFC, as a glue resinmodified with NFC as a strength agent.

TABLE 24 Additional Exemplary NFC Containing Ply-Bonding AdhesiveCompositions Material Components PVOH Based 5.5% PVOH + 0.048% NFC(Total solids 5.548%) Viscosity 0.1% NFC + 1.35% XG Modifier/ (totalsolids 1.45%) NFC Based PVOH/Viscosity 2.9% PVOH + 0.675% XG + 0.05%Modifier/ NFC (total solids 3.625%) NFC Based

Cellulose/Polyol Adhesives

In addition to the ply-bonding adhesives described above, NFC containingadhesives based on NFC/Water Soluble Cellulose/Water Soluble Polyols andadditional NFC containing adhesives may be used in the convertingprocesses described herein and illustrated in the Figures. In general,these are aqueous, NFC containing adhesive comprising: (a) water; (b)nanofibrillated cellulose; and (c) one or more of: (i) a water-solublecellulose derivative; or (ii) a water soluble polyol; and (iii) aviscosity modifier other than a water soluble cellulose derivative.Adhesives having the features enumerated in Tables 25-29 and describedbelow may be used for ply-bonding CWP, TAD and structured sheetproducts. The adhesives are typically formulated by dilutingconventional adhesives and adding NFC and another modifier or combiningNFC with viscosity modifiers as described herein. “PolymerGC Glue” inTables 25, 26 and 28 refers to glue material made up primarily ofglycols such as PEG and water soluble cellulose derivatives as isdescribed generally in U.S. Pat. No. 6,342,297 to LaBrash. For the gluecomponents (other than water), weight percent refers to weight percentsolids. The Glycol:Cellulose derivative weight ratios appear in thetables describing the PolymerGC Glue compositions. The PolymerGC Gluecomponents are blended with NFC to make the adhesive. The adhesives mayconsist essentially of the listed components.

TABLE 25 Representative PolymerGC Glue based NFC Containing AdhesivesComponent General Typical PolymerGC Glue (wt %) 1.5-7  2-6 NFC (wt %)0.025-0.5  0.035-0.35  PolymerGC Glue:NFC  5-125  10-120 Weight RatioGlycol:CellD Weight  2-10 3-7 Ratio Water (wt %) 90-99 94-98 Otheradditives balance balance

TABLE 26 Representative PolymerGC Glue, Viscosity Modifier Based NFCContaining Adhesives Component General Typical PolymerGC Glue (wt %) 1-52-4 Viscosity Modifier (wt %) 0.25-3   0.4-2  NFC (wt %) 0.25-1  0.4-0.7 PolymerGC Glue:NFC  1-25  1-10 Weight Ratio Glycol:CellD Weight 2-10 3-7 Ratio Water (wt %) 90-99 95-98 Other additives balance balance

TABLE 27 Representative Viscosity Modifier Based NFC ContainingAdhesives Component General Typical Viscosity Modifier (wt %) 0.05-2  0.075-1.5  NFC (wt %) 0.05-0.75 0.075-0.65 NFC:Viscosity Modifier 2.5%-1000%   7%-500% Weight Ratio (%) Water (wt %) 95-99   97-98.5Other additives balance balance

TABLE 28 Representative PolymerGC Glue/NFC/Viscosity ModifierCompositions with NFC:Viscosity Modifier Ratios of <100% ComponentGeneral Typical Viscosity Modifier (wt %) 0.3-2 0.5-1.5 NFC (wt %)0.025-0.2  0.035-0.15  Weight Ratio,  2.5%-75%  3%-15% NFC:ViscosityModifier Ratio (%) PolymerGC Glue (wt %) 0.5-5  1-3.5 Glycol:CellDWeight   2-10 3-7 Ratio Water (wt %) >90 >95 Other additives balancebalance

TABLE 29 Representative NFC Viscosity Modifier Compositions withNFC:Viscosity Modifier Ratios of <100% Component General TypicalViscosity Modifier (wt %) 0.3-3  0.5-1.5 NFC (wt %) 0.05-0.2 0.75-0.15Weight Ratio,  2.5%-75%  3%-15% NFC:Viscosity Modifier Ratio (%) Water(wt %) >90 >95 Other additives balance balance

In Tables 26 through 29, as well as throughout this disclosure,“viscosity modifier” refers to xanthan gum, carboxymethylcellulose,pectin and the like as herein described. Percentages in the above Tables25-29 are based on the weight of the recited component and based on theweight of the aqueous composition, except that in Tables 27, 28 and 29the NFC: modifier ratio in percent is the weight ratio of the twocomponents times 100%.

In Tables 25, 26 and 28, “CellD” (and throughout) refers to watersoluble cellulose derivatives which include cellulose ethers,hydroxyethyl cellulose, hydroxyethyl cellulose (hydrophobicallymodified), hydroxypropyl cellulose, hydroxy propyl methyl cellulose,hydroxy propyl ethyl cellulose, hydroxymethyl cellulose, methylcellulose, ethyl cellulose, methyl ethyl cellulose, ethylhydroxyethylcellulose, cyanoethylcellulose, cellulose gum, carboxymethylcellulose,carboxymethyl hydroxyethyl cellulose, calcium carboxymethylcellulose,sodium carboxymethylcellulose, and the like. Commercially availablecellulose derivatives include Klucel® from Aqualon which ishydroxypropylcellulose; Methocel® from Dow Chemical Co. which ishydroxypropyl methyl cellulose; and Cellosize® QP 100MH from UnionCarbide which is hydroxyethylcellulose that has been surface treated tobe water dispersible or quick processed having a viscosity of about100,000 cps with 2% solids. J-75MS® from Dow Chemical ishydroxypropylmethyl cellulose which has been surface treated and has a2% solution viscosity of 75,000 cps. CMC 7H® from Aqualon is sodiumcarboxymethylcellulose having a high viscosity range. A preferred watersoluble cellulose derivative is hydroxy propyl cellulose, preferablyhydroxy propyl methyl cellulose. The water soluble cellulose derivativeis present in the composition in an amount of at least about 0.5 toabout 2% by weight, preferably about 0.8 to about 1.0% by weight.

“Water soluble polyols” to make the composition of the present inventioninclude water soluble monomeric polyol, water soluble polymeric polyol,especially including PEG, functionalized polymeric polyol andcombinations thereof.

The water soluble monomeric polyol includes any polyol such as diol,triol, tetraol and combinations thereof, having a molecular weight ofless than 400. Examples of water soluble monomeric polyol are glycerin,propylene glycol, diethylene glycol, dipropylene glycol, triethyleneglycol and tetramethylene glycol. Commercially available glycols includewater soluble 75-H series, UCON lubricants from Union Carbide.

The water soluble polymeric polyol includes polyols having molecularweights from about 400 to about 12,000, preferably about 400 to about10,000 or optionally up to 8,000. The water soluble polymeric polyolincludes water soluble polymeric polyol such as polyethylene glycol,polypropylene glycol and mixtures thereof. Commercially availableglycols include polyethylene glycols such as polyethylene glycol 8000®from Dow Chemical Co. and Carbowax® from Union Carbide, polyethylene waxemulsions and paraffin wax emulsions.

The functionalized polymeric polyol includes polyester polyol, polyetherpolyol, polyesterether polyol, polyhydroxy compounds and combinationsthereof. The functionalized polymeric polyol may be present in an amountof about 0.2% to about 5% by weight, preferably about 0.5% to 2% byweight, most preferably about 0.3% to about 1% by weight.

The functionalized polyols can be either low or high molecular weightmaterials and in general will have average hydroxyl values as determinedby ASTM E 222-67, Method B, between about 1000 and 10 and preferablybetween about 500 and 50.

The functionalized polyol component may comprise an acid graftedpolyether polyol such as polypropylene oxide grafted with for example,maleic or fumaric acid as taught in Frentzel, U.S. Pat. No. 4,460,738 orKnopf U.S. Pat. No. 4,528,334 and are incorporated herein by reference.Other polyester polyols produced from mixtures of di- and tri- or higherfunctional acid and polyol components in ratios which provide residualacid functionality as well as plural hydroxy groups may be employed.

Polyester polyol can be prepared by polyesterification of organicpolycarboxylic acid or anhydride thereof with organic polyols. Usually,the polycarboxylic acid and polyol are aliphatic or aromatic dibasicacids and diols. Any ester of the monomeric polyol and polymeric polyolcan be used. Examples of these are fatty esters of polyethylene glycolshaving a molecular weight of about 400 to about 12,000, preferably about800 to about 8,000. Suitable polyester polyols are sold by Ruco Corp.Other polyester polyol includes Myrj® 45 from ICI which is a polyoxyl 8stearate.

Alternatively, the polyol component may comprise a mixture of a polyolfree of acid functionality and an acid functional compound havinghydroxy, amine or thiol functionality. Suitable acid functionalcompounds include hydroxy and mercaptocarboxylic acids, aminocarboxylicacids, aminohydroxycarboxylic acids, hydroxysulfonic acids,aminosulfonic acids and aminohydroxysulfonic acids. Representativenon-limiting examples of such acids include dimethylolpropionic acid,glycolic acid, thioglycolic acid, lactic acid, maleic acid,dihydroxymaleic acid, tartaric acid, dihydroxytartaric acid,2,6-dihydroxybenzoic acid, oxaluric acid, anilidoacetic acid, glycine,α-alanine, 6 aminocaproic acid, the reaction products of ethanolamineand acrylic acid, hydroxyethylpropionic acid, 2 hydroxyethanesulfonicacid and sulphanilic acid.

The most suitable functionalized polymeric polyols include polyalkyleneether polyol including thioethers, polyester polyols including

-   polyhydroxypolyesteramides, and hydroxy containing    polycaprolactones. Any suitable polyalkylene ether polyol may be    used. Included are-   polyoxytetramethylene glycol, polyoxyethyleneglycol, polypropylene    glycol and the reaction products of ethylene glycol with a mixture    of propylene oxide and ethylene oxide. Commercially available water    soluble polyethylene oxide includes Polyox® from Union Carbide.

Also useful are polyether polyols formed from the oxyalkylation ofvarious polyols. For example, glycols such as ethylene glycol, 1,6hexanediols, Bisphenol A and the like, higher polyols such astrimethylolpropane, trimethylethane, pentaerythritol and the like.Polyols of higher functionality which can be utilized as indicated canbe made for instance by oxyalkylation of compounds such as sorbitol orsucrose. One commonly utilized oxyalkylation method is by reacting apolyol with an alkylene oxide, for example, ethylene or propylene oxidein the presence of an acidic or a basic catalyst.

The polyhydroxy compounds can have a molecular weight of at least about400 to about 3,000, preferably about 1,000 to about 2,000. Examples ofpolyhydroxy compounds include sorbitol, mannitol, corn syrup, dextrin,fructose, sucrose and combinations thereof. The polyhydroxy compound ispresent in an amount of about 0.5% to about 5% by weight, morepreferably about 0.5 to about 3% by weight.

In practice, the adhesive contents designated PolymerGC Glue in Tables25, 26, 28 are actually diluted commercial adhesives based mostly on PEGand water soluble cellulose derivatives as noted above. Weight percentsrefer to the percentage of solids which approximates glycol andcellulose levels. In particular, the weight percent PolymerGC Glue isbased on diluted solids content in commercial adhesive compositions,such as Fuller WB4955MX2 and WB4959 which are predominantly PEG andcellulose based compositions. The solids content of these compositionsin the adhesives is thus referred to as PolymerGC Glue.

Summary of Preferred Embodiments

There is thus provided in accordance with the present invention aply-bonding agent or adhesive composition characterized by a viscosityand a surface tension for the manufacture of multi-ply paper tissue andmulti-ply paper towel comprising: (a) water; (b) nanofibrillatedcellulose; and (c) one or more modifiers effective to modify either orboth of (i) the viscosity of the composition or (ii) the surface tensionof the composition.

The NFC containing ply-bonding agent or adhesive composition of theinvention preferably comprises water, nanofibrillated cellulose and oneor more additional components selected from the group consisting ofcomponents (i), (ii), (iii) and (iv), wherein: (i) is PVOH; (ii) is PVOHand a viscosity modifier; (iii) is a viscosity modifier; and (iv) is aviscosity modifier and a surface tension modifier other than PVOH.

In the foregoing embodiments and in any of the embodiments describedherein, the ply-bonding agent or adhesive composition may becharacterized wherein the composition includes a viscosity modifier;wherein the viscosity modifier comprises a polysaccharide; wherein theviscosity modifier comprises xanthan gum; wherein the viscosity modifiercomprises carboxymethylcellulose; or wherein the viscosity modifier isselected from pectin, collagen, furcellaran, gelatin, methylcellulose,ethylcellulose, hydroxyethylcellulose, carboxy ethylcellulose, naturalrosins, corn starch, potato starch, arrowroot, ethoxylated linearalcohols, polyethylene glycols, polypropylene glycols, agar, alginicacid, and sodium alginate, carrageenan, gum arabic from the sap ofAcacia trees, gum ghatti from the sap of Anogeissus trees, gumtragacanth from the sap of astragalus shrubs, karaya gum from the sap ofsterculia trees, guar gum from guar beans, locust bean gum from theseeds of the carob tree, beta-glucan from oat or barley bran, chiclegum, dammar gum from the sap of dipterocarpaceae trees, glucomannan fromthe konjac plant, mastic gum obtained from the mastic tree, psylliumseed husks from the plantago plant, spruce gum, tara gum from the seedsof the tara tree, gellan gum and combinations thereof.

In the foregoing embodiments and in any of the embodiments describedherein, the ply-bonding agent or adhesive composition may becharacterized wherein the weight ratio of nanofibrillatedcellulose:viscosity modifier in the ply-bonding agent is from 1:0.05 to1:0.5; or wherein the weight ratio of nanofibrillatedcellulose:viscosity modifier in the ply-bonding agent is from 1:0.75 to1:0.35; or wherein the weight ratio of nanofibrillatedcellulose:viscosity modifier in the ply-bonding agent is from 1:0.1 to1:0.3; or wherein the weight ratio of nanofibrillatedcellulose:viscosity modifier in the ply-bonding agent is from 1:0.13 to1:0.2.

In any embodiment described herein, the ply-bonding agent or adhesivecomposition may contain a surface tension modifier and/or the amount ofwater in the aqueous composition is >90 wt. % based on the weight of thecomposition.

In many cases the surface tension modifier comprises a PVOH, such aswherein PVOH is present in an amount of from 0.5 percent by weight to 3percent by weight based on the weight of the aqueous composition; orwherein the weight ratio of nanofibrillated cellulose:PVOH is greaterthan 0.2; or wherein the weight ratio of nanofibrillated cellulose:PVOHis greater than 0.3 or wherein the weight ratio of nanofibrillatedcellulose:PVOH is greater than 0.4, greater than 0.5, greater than 0.6or in general wherein the weight ratio of nanofibrillated cellulose:PVOHis greater than 0.2 and up to 2.

Alternatively, the surface tension modifier may be a surface tensionmodifier other than PVOH. The surface tension modifier may be selectedfrom surfactants and water soluble polymers. Specifically, in somepreferred embodiments the surface tension modifier comprises a nonionicsurfactant.

In any of the embodiments described herein the ply-bonding agent oradhesive composition may be characterized wherein nanofibrillatedcellulose is present in an amount of greater than 0.4 percent by weightbased on the weight of the aqueous composition or whereinnanofibrillated cellulose is present in an amount of greater than 0.4percent by weight based on the weight of the aqueous composition and upto 1.5 percent by weight based on the weight of the aqueous composition.

Likewise, in any of the embodiments described herein the ply-bondingagent or adhesive composition may be characterized wherein thecomposition contains from 0.25 percent by weight to 3 percent by weightof nanofibrillated cellulose based on the weight of the aqueouscomposition, such as wherein the composition contains from 0.25 percentby weight to 2.5 percent by weight of nanofibrillated cellulose based onthe weight of the aqueous composition; or wherein the compositioncontains from 0.35 percent by weight to 1.5 percent by weight ofnanofibrillated cellulose based on the weight of the aqueouscomposition; or wherein the ply-bonding agent contains from 0.35 percentby weight to 1 percent by weight of nanofibrillated cellulose based onthe weight of the aqueous composition; or wherein the ply-bonding agentcontains from 0.35 percent by weight to 0.75 percent by weight ofnanofibrillated cellulose based on the weight of the aqueouscomposition.

In any embodiment described herein (unless otherwise specified), theply-bonding agent or adhesive composition may be characterized whereinthe composition contains from 0.4 percent by weight to 0.6 percent byweight of nanofibrillated cellulose based on the weight of the aqueouscomposition.

In any embodiment described herein, the ply-bonding agent or adhesivecomposition may be characterized wherein the composition has a surfacetension of less than 60 mN/m; or wherein the composition has a surfacetension of less than 55 mN/m.

In any embodiment described herein, the nanofibrillated cellulose mayhave a Characteristic Breaking Length of at least 3 km, such as aCharacteristic Breaking Length of from 3 km to 10 km or from 4.5 km to 9km; or from 6.5 km to 7.5 km. So, also, the nanofibrillated cellulosemay have a Characteristic Nanofiber Viscosity of greater than 15,000 cPat a shear rate of 5 sec⁻¹ and a Characteristic Nanofiber Viscosity ofless than 2,000 cP at a shear rate of 500 sec⁻¹; and/or thenanofibrillated cellulose may exhibit a Characteristic NanofiberViscosity reduction of at least 60% as the shear rate is increased from5 sec⁻¹ to 500 sec⁻¹; and/or the nanofibrillated cellulose exhibits aCharacteristic Nanofiber Viscosity reduction of at least 70%, 80% or 90%as the shear rate is increased from 5 sec⁻¹ to 500 sec⁻¹.

In any embodiment described herein, the ply-bonding agent or adhesivecomposition may contain an anti-microbial additive. The anti-microbialadditive may comprise potassium sorbate; sorbic acid; sodium sorbate;calcium sorbate; benzoic acid; calcium benzoate; potassium benzoate;sodium benzoate; calcium hydrogen sulphite; calcium sulphite; potassiumbisulphite; potassium metabisulphite; potassium sulphite; sodiumbisulphite; sodium metabisulphite; sodium sulphite; sulphur dioxide;potassium nitrate; potassium nitrite; sodium nitrate; sodium nitrite;calcium propionate; potassium propionate; propionic acid; sodiumpropionate; and mixtures thereof. Especially preferred is potassiumsorbate.

In any embodiment described herein, the ply-bonding agent or adhesivemay further contain a tackifier; a crosslinker; an insolubilizer; afiller; a second viscosity modifier; a water-resistance additive; aflame retardant; a lubricant; a softening agent; a pigment; a dye; anantioxidant; a UV-stabilizer; a resin; a rosin; a wax; a flowing agent;a compatibilizer; an aroma; or combinations thereof.

In another aspect of the invention, there is provided a method of makingabsorbent sheet comprising: (a) feeding a first absorbent cellulosic toan embossing nip; (b) embossing a pattern of raised embossments in saidfirst basesheet; (c) applying an aqueous ply-bonding agent according toany of the embodiments described herein to the raised embossments ofsaid first sheet; and (d) plying a second absorbent cellulosic sheetwith said first sheet by pressing said second cellulosic sheet to theply-bonding agent disposed on the raised embossments of said firstcellulosic sheet. The ply-bonding agent may be applied between the pliesin a discontinuous pattern, optionally wherein the discontinuous patterncorresponds to a pattern of raised embossments on one of the absorbentplies of cellulosic sheet. The method may further comprise plying athird cellulosic basesheet with said first and second cellulosicbasesheets without additional adhesive.

Another aspect of the invention is directed to a multi-ply absorbentsheet comprising: (a) a first absorbent ply of cellulosic sheet; (b) asecond absorbent ply of cellulosic sheet; and (c) a ply-bonding agentinterposed between said first absorbent ply and said second absorbentply, said ply-bonding agent adhering said absorbent plies together,wherein said ply-bonding agent comprises nanofibrillated cellulose and aviscosity modifier. The multi-ply absorbent sheet is a multi-ply tissuesheet composed predominantly of hardwood papermaking fiber, or themulti-ply absorbent sheet is a multi-ply towel sheet composedpredominantly of softwood fiber. The multi-ply absorbent sheet may havea basis weight of from 20 to 40 lbs/3000 ft² ream. Optionally, themulti-ply absorbent sheet comprises a third absorbent ply of cellulosicsheet plied together with the first and second ply.

In still yet another aspect of the invention, there is provided a methodof making multi-ply absorbent sheet comprising: (a) providing a firstabsorbent cellulosic basesheet; (b) providing a second absorbentcellulosic basesheet, wherein at least one of said first absorbentcellulosic basesheet or said second absorbent cellulosic basesheet istreated with a debonder composition; (c) interposing an NFC containingply-bonding adhesive between said first absorbent cellulosic basesheetand said second absorbent cellulosic basesheet, wherein the NFCcontaining ply-bonding adhesive comprises nanofibrillated cellulose andone or more additional components selected from the group consisting ofcomponents (i), (ii), (iii) and (iv), wherein: (i) is PVOH; (ii) is PVOHand a viscosity modifier; (iii) is a viscosity modifier and (iv) is aviscosity modifier and a surface tension modifier other than PVOH; and(d) plying said first absorbent cellulosic basesheet with said secondabsorbent cellulosic basesheet by pressing them together with the NFCcontaining ply-bonding adhesive interposed therebetween. The method maycomprise (a) feeding said first absorbent cellulosic basesheet to anembossing nip; (b) embossing a pattern of raised embossments in saidfirst absorbent cellulosic basesheet; (c) applying the NFC containingply-bonding adhesive to the raised embossments of said first absorbentcellulosic basesheet; and (d) plying said second absorbent cellulosicbasesheet with said first absorbent cellulosic basesheet by pressingsaid second absorbent cellulosic basesheet to the adhesive disposed onthe raised embossments of said first absorbent cellulosic basesheet.

In any method of making a multi-ply absorbent sheet in accordance withthe invention the NFC ply-bonding agent or adhesive may have theattributes described in any embodiment directed to the ply-bonding agentor adhesive composition herein. So, also, in any method of makingmulti-ply absorbent sheet in accordance with the invention, the processmay be characterized wherein the multi-ply basesheet comprises a thirdabsorbent cellulosic basesheet plied together with the first and secondply; wherein the ply-bonding adhesive is interposed only between twoplies prior to lamination; wherein at least one of the first absorbentcellulosic basesheet or the second absorbent cellulosic basesheet istreated with debonder composition by incorporating the debondercomposition into an aqueous furnish used to prepare the basesheet;wherein at least one of the first absorbent cellulosic basesheet or thesecond cellulosic basesheet are treated with debonder composition in anamount of from 1 lb of debonder composition per ton of cellulosicpapermaking fiber used to make the basesheet to 16 lbs of debondercomposition per ton of papermaking fiber used to make the basesheet,such as wherein at least one of the first absorbent cellulosic basesheetor the second cellulosic basesheet are treated with debonder compositionin an amount of from 2 lbs of debonder composition per ton of cellulosicpapermaking fiber used to make the basesheet to 10 lbs of debondercomposition per ton of papermaking fiber used to make the basesheet; orwherein at least one of the first absorbent cellulosic basesheet or thesecond cellulosic basesheet are treated with debonder composition in anamount of from 3 lbs of debonder composition per ton of cellulosicpapermaking fiber used to make the basesheet to 8 lbs of debondercomposition per ton of papermaking fiber used to make the basesheet; orwherein at least one of the first absorbent cellulosic basesheet or thesecond cellulosic basesheet are treated with debonder composition in anamount of from 4 lbs of debonder composition per ton of cellulosicpapermaking fiber used to make the basesheet to 6 lbs of debondercomposition per ton of papermaking fiber used to make the basesheet;and/or wherein the first basesheet and the second basesheet are treatedwith debonder composition in amounts noted above; and/or wherein thefirst basesheet and the second basesheet are treated with debondercomposition by incorporating the debonder composition into aqueousfurnish used to prepare the first and second basesheets in the amountsnoted above. In cases where a three-ply product is provided, the firstbasesheet, the second basesheet and the third basesheet may be treatedwith debonder composition in amounts recited above and the firstbasesheet, the second basesheet and the third basesheet are treated withdebonder composition by incorporating the debonder composition intoaqueous furnish used to prepare the basesheets.

The debonder composition may include a surfactant selected from nonionicsurfactants and quaternary ammonium surfactants. The quaternary ammoniumsurfactant may be selected from the group consisting of adialkyldimethyl-ammonium salts of the formula:

a bis-dialkylamidoammonium salt of the formula:

a dialkylmethylimidazolinium salt of the formula:

wherein each R may be the same or different and each R indicates ahydrocarbon chain having a chain length of from about twelve to abouttwenty-two carbon atoms and may be saturated or unsaturated; and whereinsaid compounds are associated with a suitable anion.

In any embodiment, the debonder composition comprises a nonionicsurfactant selected from alkoxylated fatty acids and alkoxylated fattyalcohols which may be the reaction product of a fatty acid or fattyalcohol with ethylene oxide.

Another aspect of the invention is directed to a method of making amulti-ply absorbent sheet according to any of the methods describedherein, wherein the multi-ply absorbent sheet has a basis weight of from12 to 60 lbs/3000 ft².

Some preferred ply-bonding agents or cellulosic compositions that can beused in connection with any embodiment are those wherein the NFCcontaining ply-bonding composition contains PVOH and NFC and NFC ispresent in an amount of from 1% to 20% based on the weight of PVOH inthe composition; wherein the NFC containing ply-bonding adhesivecontains PVOH and NFC and NFC is present in an amount of from 1.5% to 8%based on the weight of PVOH in the composition; wherein the NFCcontaining poly-bonding adhesive comprises from 1.5% to 6% by weightpolyvinyl alcohol; wherein the NFC containing ply-bonding adhesivecomprises from 90-98.5% by weight of the composition water, from 1.5% to6% by weight of the composition polyvinyl alcohol and from 1% to 30% byweight of nanofibrillated cellulose based on the weight of poly vinylalcohol in the adhesive; wherein the NFC containing ply-bonding adhesivecomprises from 94-98.5% by weight of the composition water, from 1.5% to6% by weight of the composition polyvinyl alcohol and from 1% to 30% byweight of nanofibrillated cellulose based on the weight of poly vinylalcohol in the adhesive.

Additional preferred ply-bonding agents that can be used in anyembodiment may be those wherein the composition comprises: (a) water;(b) polyvinyl alcohol; and (c) nanofibrillated cellulose, and whereinthe NFC ply-bonding adhesive comprises from 90-98.5% by weight of thecomposition water, from 0.5% to 10% by weight of the compositionpolyvinyl alcohol and from 0.05% to 2.5% by weight of the compositionnanofibrillated cellulose, optionally wherein the weight ratio ofnanofibrillated cellulose:PVOH is greater than 0.025 and up to 2; orwherein the weight ratio of nanofibrillated cellulose:PVOH is greaterthan 0.25 and up to 2. These compositions may be characterized whereinnanofibrillated cellulose is present in an amount of greater than 0.4percent by weight based on the weight of the aqueous composition and upto 1.5 percent by weight based on the weight of the aqueous composition.

Still other preferred compositions which can be utilized in anyembodiment are those wherein the aqueous NFC containing ply-bondingadhesive comprises from 2.5 wt % to 6 wt % PVOH based on the weight ofthe composition, greater than 90 wt % water based on the weight of thecomposition and from 1% to 20% NFC based on the weight of the PVOH inthe composition; or wherein the aqueous NFC containing ply-bondingadhesive comprises from 1 wt % to 3 wt % PVOH, from 0.25 wt % to 1 wt %NFC and greater than 95 wt % water wherein the content of PVOH, NFC andwater is based on the weight of the composition; or wherein the NFCcontaining ply-bonding adhesive comprises from 0.15 wt % to 3 wt % NFC,a viscosity modifier and greater than 90 wt % water wherein the contentof NFC and water are based on the weight of the composition, and whereinthe viscosity modifier is present in an amount such that the weightratio of NFC:viscosity modifier is from 2.5 to 10; and/or wherein theNFC containing ply-bonding adhesive contains PVOH and NFC and NFC ispresent in an amount of from 15% to 45% based on the weight of PVOH inthe composition.

Other compositions that can be utilized in any embodiment include thosewherein the NFC containing ply-bonding adhesive contains NFC and aviscosity modifier, such as wherein the weight ratio of NFC:viscositymodifier in the NFC containing ply-bonding adhesive is from 2.5 to 10;or wherein the weight ratio of NFC:viscosity modifier in the NFCcontaining ply-bonding adhesive is from 4 to 8; or wherein the percentweight ratio of NFC:viscosity modifier is from 5% to 10%; or wherein thepercent weight ratio of NFC:viscosity modifier is from 200% to 750%.

A significant advantage of using the ply-bonding compositions of theinvention is the increased capability of tolerating higher convertingspeed. The methods of making multi-ply absorbent sheet of the inventionare thus characterized by processes wherein the basesheet is convertedto multi-ply absorbent sheet at a converting speed of greater than 1000fpm; wherein the basesheet is converted to multi-ply absorbent sheet ata converting speed of greater than 1250 fpm; wherein the basesheet isconverted to multi-ply absorbent sheet at a converting speed of greaterthan 1500 fpm; wherein the basesheet is converted to multi-ply absorbentsheet at a converting speed of greater than 1750 fpm; generally whereinthe basesheet is converted to multi-ply absorbent sheet at a convertingspeed of from 1000 fpm to 2250 fpm.

Products include multi-ply absorbent sheet comprising: (a) a firstabsorbent ply of absorbent cellulosic basesheet; (b) a second absorbentply of absorbent cellulosic basesheet, wherein at least one of saidfirst absorbent ply of absorbent cellulosic basesheet or said secondabsorbent ply of cellulosic basesheet is treated with a debondercomposition; (c) an NFC containing ply-bonding adhesive interposedbetween said first absorbent ply and said second absorbent ply, saidply-bonding adhesive adhering said absorbent plies together, whereinsaid NFC containing ply-bonding adhesive comprises nanofibrillatedcellulose and one or more additional components selected from the groupconsisting of components (i), (ii), (iii) and (iv), wherein: (i) isPVOH; (ii) is PVOH and a viscosity modifier; (iii) is a viscositymodifier and (iv) is a viscosity modifier and a surface tension modifierother than PVOH. The adhesive may be applied between the plies in adiscontinuous pattern, such as wherein the discontinuous patterncorresponds to a pattern of raised embossments on one of the absorbentplies of cellulosic sheet.

One method of making absorbent sheet in accordance with the inventioncomprises (a) providing a first absorbent cellulosic basesheet; (b)providing a second absorbent cellulosic basesheet; (c) interposing anNFC containing ply-bonding adhesive between said first absorbentcellulosic basesheet and said second absorbent cellulosic basesheet,wherein the NFC containing ply-bonding adhesive comprisesnanofibrillated cellulose and one or more additional components selectedfrom the group consisting of components (i), (ii), (iii), (iv) and (v)wherein (i) is a water-soluble cellulose derivative; (ii) is a watersoluble polyol; (iii) is a viscosity modifier other than a water solublecellulose derivative; (iv) is PVOH; and (v) is PVOH and a viscositymodifier; said NFC containing ply-bonding adhesive optionally including(vi) a surface tension modifier other than PVOH; and (d) plying saidfirst absorbent cellulosic basesheet with said second absorbentcellulosic basesheet by pressing them together with the NFC containingply-bonding adhesive interposed therebetween. One preferred NFCcontaining ply-bonding adhesive used in the process comprises one ormore of: (i) a water soluble cellulose derivative; (ii) a water solublepolyol; and (iii) a viscosity modifier other than a water solublecellulose derivative. The water soluble polyol employed may bepolyethylene glycol, optionally having a molecular weight of from 400 to10,000 Daltons. When a water soluble cellulose derivative is used, thewater soluble cellulose derivative is optionally selected fromhydroxypropyl methyl cellulose and hydroxypropyl cellulose.

The present invention thus also encompasses an adhesive comprisingwater, nanofibrillated cellulose and one or more additional componentsselected from the group consisting of components (i), (ii), (iii), (iv)and (v) wherein (i) is a water-soluble cellulose derivative; (ii) is awater soluble polyol; (iii) is a viscosity modifier other than a watersoluble cellulose derivative; (iv) is PVOH; and (v) is PVOH and aviscosity modifier; said NFC containing ply-bonding adhesive optionallyincluding (vi) a surface tension modifier other than PVOH. Any of thecomponents may be present in amounts noted herein.

Also included are multiply products incorporating the adhesivecomprising: (a) a first absorbent ply of absorbent cellulosic basesheet;(b) a second absorbent ply of absorbent cellulosic basesheet, whereinoptionally at least one of said first absorbent ply of absorbentcellulosic basesheet or said second absorbent ply of cellulosicbasesheet is treated with a debonder composition; (c) an NFC containingply-bonding adhesive interposed between said first absorbent ply andsaid second absorbent ply, said ply-bonding adhesive adhering saidabsorbent plies together, wherein said NFC containing ply-bondingadhesive comprises nanofibrillated cellulose and one or more additionalcomponents selected from the group consisting of components (i), (ii),(iii), (iv) and (v) wherein (i) is a water-soluble cellulose derivative;(ii) is a water soluble polyol; (iii) is a viscosity modifier other thana water soluble cellulose derivative; (iv) is PVOH; and (v) is PVOH anda viscosity modifier; said NFC containing ply-bonding adhesiveoptionally including (vi) a surface tension modifier other than PVOH.

In any embodiment, including processes of making multi-ply absorbentproducts and the products so made, an adhesive comprising (a) water; (b)nanofibrillated cellulose; (c) one or more of: (i) a water-solublecellulose derivative; or (ii) a water soluble polyol; and (iii) aviscosity modifier other than a water soluble cellulose derivative maybe employed. The water soluble polyol may be a polyethylene glycol,suitably having a molecular weight of from 400 to 10,000 Daltons;whereas the water soluble cellulose derivative is selected fromhydroxypropyl methyl cellulose and hydroxypropyl cellulose. The othercomponents may be present or absent; if present they are present inamounts and having the characteristics of any embodiment describedherein.

One preferred adhesive comprises: (a) greater than 90 wt % water; (b)water soluble polyol and a water soluble cellulose derivative present inan aggregate amount of from 1.5 wt % to 7 wt %, wherein the weight ratioof water soluble polyol to water soluble cellulose derivative is from 2to 10; and (c) nanofibrillated cellulose present in an amount of from0.025 wt % to 0.5 wt %, wherein the weight ratio of water soluble polyoland water soluble cellulose derivative collectively to NFC is from 5 to125.

Another preferred adhesive comprises: (a) greater than 90 wt % water;(b) a viscosity modifier other than a water soluble cellulose derivativepresent in an amount of from 0.25% to 3 wt %; (c) water soluble polyoland a water soluble cellulose derivative present in an aggregate amountof from 1 wt % to 5 wt %, wherein the weight ratio of the water solublepolyol to the water soluble cellulose derivative is from 2 to 10; and(d) nanofibrillated cellulose present in an amount of from 0.25 wt % to1 wt %, wherein the weight ratio of water soluble polyol and watersoluble cellulose derivative collectively to NFC is from 1 to 25.

Yet another preferred adhesive comprises: (a) 95 wt % or more water; (b)NFC present in an amount of from 0.05 wt % to 0.75 wt %; and (c) aviscosity modifier present in an amount of from 0.05 wt % to 2 wt %,wherein the percent weight ratio of NFC:viscosity modifier is from 2.5%to 1000%.

Still yet another adhesive comprises: (a) greater than 90 wt % water;(b) water soluble polyol and a water soluble cellulose derivativepresent in an aggregate amount of 0.5 wt % to 5 wt % wherein the weightratio of the water soluble polyol to the water soluble cellulosederivative is from 2 to 10; (c) nanofibrillated cellulose in an amountof from 0.025 wt % to 0.2 wt %; and (d) a viscosity modifier other thana water soluble cellulose derivative present in an amount of from 0.3 wt% to 2 wt %, wherein the percent weight ratio of NFC:viscosity modifierother than water soluble cellulose derivative is from 2.5% to 75%.

A further adhesive composition which may be employed comprises:

(a) greater than 90 wt % water; (b) nanofibrillated cellulose present inan amount of from 0.05 wt % to 0.2 wt %; and (c) a viscosity modifierpresent in an amount of from 0.3% to 3 wt %, wherein the percent weightratio of NFC:viscosity modifier is from 2.5% to 75%.

While the invention has been described in detail, modifications withinthe spirit and scope of the invention will be readily apparent to thoseof skill in the art. Such modifications are also to be considered aspart of the present invention. In view of the foregoing discussion,relevant knowledge in the art and references discussed above inconnection with the Background of the Invention, the disclosures ofwhich are all incorporated herein by reference, further description isdeemed unnecessary. In addition, it should be understood from theforegoing discussion that aspects of the invention and portions ofvarious embodiments may be combined or interchanged either in whole orin part. Furthermore, those of ordinary skill in the art will appreciatethat the foregoing description is by way of example only, and is notintended to limit the invention.

What is claimed is:
 1. A ply-bonding agent or adhesive compositioncharacterized by a viscosity and a surface tension for the manufactureof paper tissue and paper towel, said composition comprising: (a) water;(b) nanofibrillated cellulose; and (c) one or more modifiers effectiveto modify either or both of (i) the viscosity of the composition or (ii)the surface tension of the composition, wherein the one or moreadditional modifiers are selected from the group consisting ofcomponents (iii), (iv), (v), (vi), (vii) or (viii), wherein: (iii) isPVOH and a viscosity modifier; (iv) is a viscosity modifier; (v) is aviscosity modifier and a surface tension modifier other than PVOH; (vi)is a water-soluble cellulose derivative; (vii) is a water solublepolyol; and (viii) is a surface tension modifier other than PVOH.
 2. Theply-bonding agent or adhesive composition according to claim 1, whereinthe composition includes a viscosity modifier.
 3. The ply-bonding agentor adhesive composition according to claim 2, wherein the viscositymodifier comprises a polysaccharide.
 4. The ply-bonding agent oradhesive composition according to claim 2, wherein the viscositymodifier comprises xanthan gum.
 5. The ply-bonding agent or adhesivecomposition according to claim 2, wherein the viscosity modifiercomprises carboxymethylcellulose.
 6. The ply-bonding agent or adhesivecomposition according to claim 2, wherein the weight ratio ofnanofibrillated cellulose:viscosity modifier in the ply-bonding agent oradhesive composition is from 1:0.05 to 1:0.5.
 7. The ply-bonding agentor adhesive composition according to claim 2, wherein the weight ratioof nanofibrillated cellulose:viscosity modifier in the ply-bonding agentor adhesive composition is from 1:0.13 to 1:0.2.
 8. The ply-bondingagent or adhesive composition according to claim 2, wherein PVOH ispresent in an amount of from 0.5 percent by weight to 3 percent byweight based on the weight of the aqueous composition.
 9. Theply-bonding agent or adhesive composition according to claim 2, whereinthe ply-bonding agent contains a surface tension modifier selected fromsurfactants and water soluble polymers.
 10. The ply-bonding agent oradhesive composition according to claim 1, wherein the ply-bonding agentor adhesive composition includes at least one of a viscosity modifier ora surface tension modifier other than PVOH and contains from 0.25percent by weight to 3 percent by weight of nanofibrillated cellulosebased on the weight of the aqueous composition.
 11. The ply-bondingagent or adhesive composition according to claim 10, wherein thecomposition contains from 0.35 percent by weight to 1.5 percent byweight of nanofibrillated cellulose based on the weight of the aqueouscomposition.
 12. The ply-bonding agent or adhesive composition accordingto claim 1, wherein said nanofibrillated cellulose has a CharacteristicBreaking Length of at least 3 km.
 13. The ply-bonding agent or adhesivecomposition according to claim 1, wherein said nanofibrillated cellulosehas a Characteristic Nanofiber Viscosity of greater than 15,000 cP at ashear rate of 5 sec⁻¹ and a Characteristic Nanofiber Viscosity of lessthan 2,000 cP at a shear rate of 500 sec⁻¹.
 14. A method of makingmulti-ply absorbent sheet comprising: (a) providing a first absorbentcellulosic basesheet; (b) providing a second absorbent cellulosicbasesheet, (c) interposing a ply-bonding agent or adhesive compositionaccording to claim 1 between said first absorbent cellulosic basesheetand said second absorbent cellulosic basesheet, and (d) plying saidfirst absorbent cellulosic basesheet with said second absorbentcellulosic basesheet by pressing them together with the NFC containingply-bonding agent or adhesive composition interposed therebetween. 15.The method of making multi-ply absorbent sheet according to claim 14,wherein at least one of said first absorbent cellulosic basesheet orsaid second absorbent cellulosic basesheet is treated with a debondercomposition.
 16. The method of making multi-ply absorbent sheetaccording to claim 15, wherein at least one of the first absorbentcellulosic basesheet or the second cellulosic basesheet are treated withdebonder composition in an amount of from 1 lb of debonder compositionper ton of cellulosic papermaking fiber used to make the basesheet to 16lbs of debonder composition per ton of papermaking fiber used to makethe basesheet.
 17. The method of making a multi-ply absorbent sheetaccording to claim 15, wherein at least one of the first absorbentcellulosic basesheet or the second cellulosic basesheet are treated withdebonder composition in an amount of from 2 lbs of debonder compositionper ton of cellulosic papermaking fiber used to make the basesheet to 10lbs of debonder composition per ton of papermaking fiber used to makethe basesheet.
 18. The method of making a multi-ply absorbent sheetaccording to claim 15, wherein at least one of the first absorbentcellulosic basesheet or the second absorbent cellulosic basesheet istreated with debonder composition by incorporating the debondercomposition into an aqueous furnish used to prepare the basesheet. 19.The method of making a multi-ply absorbent sheet according to claim 15,wherein the debonder composition comprises a surfactant selected fromnonionic surfactants and quaternary ammonium surfactants and mixturesthereof.
 20. A multi-ply absorbent sheet comprising: (a) a firstabsorbent ply of absorbent cellulosic basesheet; (b) a second absorbentply of absorbent cellulosic basesheet, wherein at least one of saidfirst absorbent ply of absorbent cellulosic basesheet or said secondabsorbent ply of cellulosic basesheet is treated with a debondercomposition; (c) a ply-bonding agent or adhesive composition accordingto claim 1 interposed between said first absorbent ply and said secondabsorbent ply, said ply-bonding agent or adhesive composition adheringsaid absorbent plies together.
 21. A method of making multi-plyabsorbent sheet comprising: (a) providing a first absorbent cellulosicbasesheet; (b) providing a second absorbent cellulosic basesheet,wherein at least one of the first absorbent cellulosic basesheet or thesecond cellulosic basesheet are treated with debonder composition in anamount of from 1 lb of debonder composition per ton of cellulosicpapermaking fiber used to make the basesheet to 16 lbs of debondercomposition per ton of papermaking fiber used to make the basesheet; (c)interposing an NFC containing ply-bonding adhesive between said firstabsorbent cellulosic basesheet and said second absorbent cellulosicbasesheet, wherein the NFC containing ply-bonding adhesive comprisesnanofibrillated cellulose and one or more additional components selectedfrom the group consisting of components (i), (ii), (iii) and (iv),wherein: (i) is PVOH; (ii) is PVOH and a viscosity modifier; (iii) is aviscosity modifier and (iv) is a viscosity modifier and a surfacetension modifier other than PVOH; and (d) plying said first absorbentcellulosic basesheet with said second absorbent cellulosic basesheet bypressing them together with the NFC containing ply-bonding adhesiveinterposed therebetween.
 22. The method of making a multi-ply absorbentsheet according to claim 21, wherein the process comprises: (e) feedingsaid first absorbent cellulosic basesheet to an embossing nip; (f)embossing a pattern of raised embossments in said first absorbentcellulosic basesheet; (g) applying the NFC containing ply-bondingadhesive to the raised embossments of said first absorbent cellulosicbasesheet; and (h) plying said second absorbent cellulosic basesheetwith said first absorbent cellulosic basesheet by pressing said secondabsorbent cellulosic basesheet to the adhesive disposed on the raisedembossments of said first absorbent cellulosic basesheet.
 23. The methodof making a multi-ply absorbent sheet according to claim 21, wherein themulti-ply basesheet comprises a third absorbent cellulosic basesheetplied together with the first and second ply.
 24. The method of making amulti-ply absorbent sheet according to claim 21, wherein the NFCcontaining ply-bonding adhesive comprises: (i) water; (ii) polyvinylalcohol; and (iii) nanofibrillated cellulose, and wherein the NFCply-bonding adhesive comprises from 90-98.5% by weight of thecomposition water, from 0.5% to 10% by weight of the compositionpolyvinyl alcohol and from 0.05% to 2.5% by weight of the compositionnanofibrillated cellulose.
 25. The method of making a multi-plyabsorbent sheet according to claim 24, wherein the weight ratio ofnanofibrillated cellulose:PVOH is 0.1 or greater and up to 0.5.